When you freshly install a new version, no package from your previous version will be available. You can either use raco pkg migrate or “Copy from Version” in DrRacket (in File > Package Manager) to install all packages from a previous version.
Re the error: it would be nice to get the full error message. But one possibility is that it is an error from Quickscript. Quickscript shares all scripts across all Racket versions. So if you have a script that depends on an installed package in your previous version while not having the same package installed in the current version, that would cause an error. If this is the case, after using raco pkg migrate, the error would go away.