Upvote:3
I actually had very similar happen the last time I used Ryanair - only I didn't actually discover the barcode hadn't printed until I arrived at the airport! I had printed all the boarding passes directly from the "Print" link on the site (i.e. not from a separate PDF viewer).
I was directed to the Ryanair checkin desk who indicated that apparently this, quote: "Happens a lot" and printed replacement boarding cards for me without quibble or charge.
For the return trip I downloaded the card as a pdf and then printed it and it worked fine.
Upvote:4
I've had other issues with tickets where the barcode isn't printed or even shown on the screen. My advice is to try another PDF Viewer. Acrobat Reader DC is a good start: https://get.adobe.com/reader/