Cannot set up vault in Google Drive

I’m a big fan and supporter of encryption apps but I am new to Cryptomator. I have set up Cryptomator on my iPhone and my PC and the app on both devices have been very buggy. And getting even something basic to work seems to be a hit and miss affair. On my iPhone for example, I have been unable to set up a vault in Google Drive. I get “error: unable to perform unauthorised operation”. Tried many times. Password is correct. No problem setting up a new vault in other drives. I googled the problem but have had no luck. (It’s a paid app) On my PC, the app has crashed and there were “fatal errors” re-installing it. Thoughts anyone?