If you encounter this error when trying to connect your mailbox to a Google account;
Refresh token missing. Please remove Groove from your authorized applications at: https://security.google.com/settings/security/permissions and then link your mailbox again.
then there are a few things you can do to resolve the issue;
De-authorize the Groove App, and link again
The first thing you can try is to remove any previous authorizations for the Groove app from your Google security console.
2. You will see the list of applications you have authorized to access your Google account. Click the Groove app.
3. Click Remove to revoke access to Groove.
4. Now go back to Groove, and re-authenticate with Google. NOTE: if you have multiple Google accounts, be sure to select the correct one!
At this point your mailbox should be properly linked with your Google account! However, if it still shows a "Refresh token missing" error, then read on, there are few extra steps to get it working.
Re-add the mailbox
If you're still getting an error after trying the above, then you need to get Groove to refresh the stored credentials for your mailbox. This is done by changing the email of your mailbox, and then changing it back.
1. In your mailbox settings, change the email of your mailbox to something else and press Save.
You can use any email address not connected to Google - 'email@example.com' is a dummy email address that would work;
2. Now, change the mailbox email back to your original email address (ie. the one you want to connect with Google). In the screenshot below I've used 'firstname.lastname@example.org', but you should use your own actual email here.
3. Now reconnect your mailbox with Google by clicking "Click here to complete setup". You may need to refresh the mailbox settings page for this link to appear.
4. Follow the Google authentication steps as prompted.
And your mailbox should now be connected with Google!