Mac App Store version fails to open, Safari extension works

I’m running 10.14.6. and Safari 14.1.1. Wanting to use the Safari extension I installed Bitwarden 1.27.1 from the App Store three times. Each instal opened to give a white rectangle in the middle of the screen and appeared ‘live’ but went no further. But the Safari extension worked. When I replace the App Store version with the normal version, that version runs correctly. Although I have kept the Mac Store version with a modified name, the Safari extension no longer works. Does anyone know a workaround?