Unable to complete first backup to Google Drive

I’ve just purchased a basic web license for duplicacy and I’m using it to do a backup of my home directory on Mac OSX to Google Drive.

However after 3 or 4 tries to complete the first backup, it just keeps failing.

2019-09-16 08:47:34.276 INFO BACKUP_LIST Listing all chunks
2019-09-16 09:03:17.980 INFO GCD_RETRY [0] Maximum number of retries reached (backoff: 64, attempts: 15)
2019-09-16 09:03:17.981 ERROR LIST_FILES Failed to list the directory chunks/: googleapi: Error 401: Invalid Credentials, authError

2019-09-17 09:32:07.374 INFO GCD_RETRY [0] Maximum number of retries reached (backoff: 64, attempts: 15)
2019-09-17 09:32:07.376 ERROR UPLOAD_CHUNK Failed to upload the chunk c48a0d18ebd3004251d2e323ffc00575d3068b7b1b9162a777ace5b7a55bb980: googleapi: Error 401: Invalid Credentials, authError
2019-09-17 09:32:07.576 INFO INCOMPLETE_SAVE Incomplete snapshot saved to /Users/me/.duplicacy-web/repositories/localhost/0/.duplicacy/incomplete

2019-09-18 09:07:14.681 INFO GCD_RETRY [0] Maximum number of retries reached (backoff: 64, attempts: 15)
2019-09-18 09:07:14.683 ERROR UPLOAD_CHUNK Failed to upload the chunk b022d024b2bb331c7453c50d9091ec2f949b2fd9e4fdc5d563bf2d3536f238c5: googleapi: Error 401: Invalid Credentials, authError
2019-09-18 09:07:44.718 INFO INCOMPLETE_SAVE Incomplete snapshot saved to /Users/me/.duplicacy-web/repositories/localhost/0/.duplicacy/incomplete

After each of these failures, I just the press the ‘>’ button again on the backup page, and it continues I guess, but it’s not successfully completed one backup yet.

I haven’t changed the auth-token. I guess the google-api is giving auth errors, but when I notice it’s failed, it’s quite happy to continue the backup.

Is there a solution here, or is Google Drive just not really supported?