Upvote:15
If your agent was not a Canadian lawyer or a regulated immigration consultant, they were not legally authorized under Canadian law to provide advice or direct your application for payment.
In the unlikely case that they are regulated, they must give you information and all correspondences to and from the government upon request. You may complain either to the bar association of their province (for lawyers) or the College of Immigration and Citizenship Consultants.
Unfortunately, in many cases, you cannot be even sure that they submitted your application to the Canadian government.
If you have doubts regarding the handling of your Canadian visa application by your agent, you can request a copy of your files and correspondances under the Access to Information Act from Immigration, Refugees and Citizenship Canada (IRCC, Department of Citizenship and Immigration). To file such a request, you will need the help of a Canadian friend or someone physically located in Canada. The government usually responds within two months (despite the 30-day legal deadline).
Upvote:20
Visitor visa rejection is usually not a big problem. Settlement visa is independently assessed, as the premise is different. Being denied a visitor visa before is therefore not a big deal and won't usually hurt your chances. So, you should disclose any visa rejections before.
"if will disclose this"
Being said that, if you don't disclose your rejection, its is sure that you won't get your visa and you will be likely banned from UK for a definite time, due to the act of deception. You should disclose even if you are not sure why it is rejected. There is field to add extra information to elaborate on the circumstances.