No proxy, direct connection working fine, I'm replying using it! I tried changing from system setting for proxy to none but no difference.
I can see Enpass is trying to communicate with google drive with Wireshark, as I mentioned in the first post re the TLS traffic, and it seems like something is going wrong with the exchange since there's an encrypted alert every time, but I can't easily snoop further and don't know how to get Enpass to output debug info, nor even if there is a way to do that.
I tried using Dropbox and with that I get a -116 error with no sync file in place, then the same -118 once I've synchronised the android app (v5.6.4) to create the file.
Another edit: I tried using a different account for google drive and it synchronised successfully, but once I'd done a sync to the new account with the android app then I get the -118 error from the linux prog (v5.6.3). It looks like some kind of format incompatibility.