See Parallels Forums "Quickbooks Desktop no longer working after 26.1.2 upgrade"

https://forum.parallels.com/threads/quickbooks-desktop-no-longer-working-after-26-1-2-upgrade.368876...

that refers to the Parallels Knowledge Base solution "Quickbooks Desktop application not loading"

https://kb.parallels.com/en/131061

which notes two solutions, the first of which that sets compatibility emulation settings to very strict execution has been mentioned in this thread but does not always work (it didn't work for me), while the second of which is to downgrade to Parallels v26.0.1 (which did work for me) and follow the instructions for turning off automatic update.

After I downgraded to the older Parallels version I still needed to restore from backup as I still couldn't run a company file I had earlier tried to restore when things were broken (so it may have created a corrupted company file), but restoring from backup and subsequent run/use of that company file worked and I verified that quitting QuickBooks, shutting down both Windows and Parallels, and starting up again still worked.

So while you can certainly try the simpler possible solution of changing the compatibility emulation settings, if that still doesn't work, then downgrade to Parallels v26.0.1.