You may try to hard-reset PS21 :
Rename C:\Users\Yourusername\AppData\Local\Pinnacle_Studio_21\Studio\21.0 to C:\Users\Yourusername\AppData\Local\Pinnacle_Studio_21\Studio\21.0.old
Launch Studio, open your project thanks to File menu, Open and click Export
One big side effect => your library has been reset.
If the workaround failed, delete the newly created C:\Users\Yourusername\AppData\Local\Pinnacle_Studio_21\Studio\21.0 and rename C:\Users\Yourusername\AppData\Local\Pinnacle_Studio_21\Studio\21.0.old to C:\Users\Yourusername\AppData\Local\Pinnacle_Studio_21\Studio\21.0