I've no experience (by choice!) of Ryanair but I do know a little about online check in systems and DCSs.
In addition to the good advice you've been given by others, can I suggest :
The ticket may not have been paid with your credit card. The t/a may have charged your credit card via an EFTPOS system but they may have paid Ryanair with another card.
There may be a mismatch in your name between what the agent's front office system sent you as an itinerary and what Ryanair have. For example you might be John O'Brien but to Ryanair you are John Obrien. Or it's John Robert Smith as opposed to John R Smith.
Looking for all possible sources of error will drive you nuts. I'd have a good whisky, admit defeat, and go to the airport early and prepared for the worst. You might get a pleasant surprise!
Unfortunately booking through an intermediary is fraught with difficulty.