Thank you for your replies. All my colleagues could get in into these courses before and after I got these errors. When I 'borrowed' their gotolearning links (I didn't receive mine), I still can't login (says full), but they can login before and after me (doesn't say it's full for them via the same link).
I deregistered and re-registered for the last session of today, but didn't receive a gotolearning link. We'll see... Btw, it says 'full' on all the courses now, but it didn't this morning when I registered (for all of them). It seems strange that I would not receive a registration error, Marketo registration confirmation, and see the 'join' link if I didn't register successfully.