Problems opening projects made with Cubase 9.5 in Cubase 11

Have any of you had problems opening projects made with Cubase 9.5 in Cubase 11? Because to me on some it gave me an opening error. Situation: Computer with Cubase 9.5 and Cubase 11 installed at the same time.

working here - what is the error ?

It gave me a serious error message with red X I didn’t have time to take a picture. Could it be that third party plug-ins are conflicting? Such as reverbs, eqs, etc. ?

anything is possible but it seems unlikely

not much we can do without the exact error message - see if you can take a picture next time