'Unable to find database' Capture One 20 for Sony

I started using the free C1 for Sony in November 2020 and it has worked fine, until now. When I try to open the application I get the message ‘Unable to find database. The application was unable to find the database for the catalogue’. The system prompts to ‘browse’ to select a Capture One catalogue, which I can see in Pictures, but if I click ‘open it returns the same error message.

My iMac o/s has recently been upgraded to Big Sur version 11.1 - could this have caused it? Lightroom (5!) continues to work (for my earlier Nikon images). Being somewhat non-technical I am really struggling and have not received a response so far from Capture One support.