Stories from history of mercenaries who didn't get paid

Couple of thoughts come to mind...

In the First Barbary War, The American fire brand, William Eaton, invaded Libya with 8 Marines and a locked chest which he claimed contained gold enough to pay for the 800 mercenaries which he recruited from Egypt for the task. 500 Arabs and 300 european mercenaries. In reality Jefferson who had sent Eaton on this mission didn't fund Eaton's ambitious plan of toppling the Bay of Tripoli and Eaton and the Marines jumped on an American Ship and abandoned the mercenary army after a great victory. This occurred when it was made clear to Eaton, Jefferson's government was going to snatch defeat from the jaws of victory and pay off the Bey. This episode is referenced in the U.S. Marine Corps Anthem without mentioning the Marines and Eaton abandoned the mercenaries in Libya or the Jefferson administrations culpability.

Battle of New Orleans
Not sure you would call them Mercenaries because some were volunteers and all were under the strong influences of Andrew Jackson who was not a man who easily took no for an answer. But Mercenaries would fit because included in Jackson's 4000 defenders of New Orleans who fought against 14000 british troops fresh off the battle fields of europe where they had fought Napoleon were Pirates(Pirate Jean Lafitte), Indians, and a motley crew of irregulars.

Andrew Jackson had brought a small force down from Kentucky to defend New Orleans from British attack. Along the way Jackson got word that Congress had decided not to pay for supplies either for them to continue to New Orleans or even the costs of supplies for the return trip to Kentucky. Andrew Jackson who harbored a singular hatred of the British continued to New Orleans where he found the city completely unprepared to resist the British. Jackson would recruit groups of "interested parties" to aid in his defense of new Orleans and by employing a mixed bag of irregular tactics, (ordering his sharp shooters to shoot British officers first etc)... Jackson presided over one of the most lopsided victories in American history killing 2000 British soldiers and only loosing 7 soldiers himself. Jackson of coarse would be called a hero and would eventually land in the White House for the victory.

savings new orleans

The Mamaluks
Egyptian slave soldiers who revolted against their masters and ultimately turned back the Mongol invasion of the Middle East at the battle of Battle of Ain Jalut

There's The Ten Thousand, who were hired by Cyrus the Younger, and were left without an employer when he died.

Might as well throw out the Carthage option as it's potential that the mercenary war was purposefully initiated by the Romans.

Carthage had employed a relatively large mercenary army on Sicily during the first punic war. However there was no major land battle on Sicily (Rome forced Carthage to peace with the actions of their fleet) and Hamilcar Barca (The Carthage general in Sicily) was forced to a peace despite his army being 'undefeated' on the land. Hamilcar made a few promises to his mercs of great pay for their services...when an army hires mercenaries it in part relies on attrition, less surviving mercenaries is ultimately less people to pay. Since there was no major land battle, most of the mercenaries survived the journey back to demand pay which Hamilcar had promised earlier.

https://en.wikipedia.org/wiki/Hamilcar_Barca#Hamilcar_in_Sicily

The last condition is mentioned by Polybius in place of the one regarding not making war on Syracuse. It is possible that Hamilcar Barca secured the last clause after the initial conditions, which were more favorable to Carthage, was altered by Rome with a harsher one. Hamilcar Barca gathered the Carthaginian soldiers from Drepana and Eryx at Lilybaeum, surrendered his command,[38] returned to Carthage and retired to private life, leaving Gisco and the Carthaginian government to pay off his soldiers. Whatever was the motivation behind this act, it was resented by the mercenaries left behind in Sicily.

Hard to call if avoiding a direct land engagement was intentional by the Romans (This was before the Fabian strategy was used vs Hannibal where the Romans intentionally avoided a direct battle with Hannibal), however the end result was the majority of the mercenaries survived the Punic war to return to Carthage where they would demand pay.

The “Undefeated” army now created a unique problem for Carthage. Had Hamilcar suffered a decisive defeat, casualties and prisoners would have diminished their numbers and Carthage would have had an excuse not to pay anything. But now the 20,000 man army had to be paid their full due.

The peace arrangement with Rome included a hefty amount in war reparations to Rome which heavily impacted Carthage's ability to pay these mercenaries. The mercenaries were sent in small groups to Carthage to be paid, but the Carthage gov't couldnt and the number of unpaid mercs in Carthage grew.

Carthaginian authorities then sent them off to Sicca, planning to plead with the whole army to forgo their unpaid wages by pointing out the dire financial situation of Carthage.[40] Hamilcar’s former soldiers, who had been kept together only by his personal authority and by the promise of good pay, broke out into open mutiny once Hanno the Great tried to impose this, and marched on Carthage and encamped at Tunis. The soldiers refused to accept Hamilcar as an arbitrator, angered by his refusal to accompany his army from Sicily and retiring to Carthage as soon the treaty with Rome was formalized, and although Carthage at this point conceded all their demands, things soon boiled over and started the conflict known as the Mercenary War

The mercenaries found like minded African subjects of Carthage and the mercenary war began.

As an interesting side note...the Punic wars was actually initiated by Mercenaries dragging Carthage and Rome into conflict. A group of mercenaries known as the Mamertines was employed by the Greek city state of Syracuse to fight vs the Carthaginians. The Greeks were defeated and when the self-proclaimed king died, the majority of his mercenaries found themselves unemployed on the island of Sicily. The town of Messana let the mercs in and the mercs betrayed them and slaughtered the population turning the town from a small farm town into a raiding base. The new king of Syracuse saw this threat and marched against the Mamertines and defeated them. The Mamertines plead with both Carthage and Rome for help, ultimately bringing Rome and Carthage into the conflict known as the first Punic War.

Sack of Rome (1527): The troops of Charles V had won over the French but they had been not paid. They forced their commander to march on Rome, that was taken and plundered.

This could have been disastrous for Charles, as he had posited himself as the champion of Catholicism, against Protestant movements. But in the end it seems that it helped him, since the Pope stopped trying to interfere with his policies and become way more compliant.

Sack of Antwerp: The forces of Philip II (Charles V) had declared bankruptcy and soldiers were, again, not being paid. They took matters in their own hands and plundered the rich merchant city of Antwerp.

The consequences were a reinforcement of the Dutch revolt, and the decline (and consequently loss of tax revenues) of Antwerp.

Thinks were more complicated with the business of the Catalan company in the Byzantine Empire. They were paid, but with newly issued coins that were severely debased and that they had trouble trading with. This fueled other issues that the troops had (conflicts with other mercenaries) and it came to a head when, in a meeting with the Byzantines, the Company leaders were killed. The soldiers proceeded then to fight the Byzantine troops and to ravage and plunder the country; they stayed in the Gallipoli region until they were forced to move because there was nothing left to plunder.

After that, they came into service of the Duke of Athens. After the campaign, again they were refused pay and the Duke tried to expel. The Company fought back and defeated and killed the Duke; they took control of the Duchy and expanded it, and put it under the sovereignty of the Aragonese kings.