Smartsheet Merge for Google Docs authentication error
I'm having an issue with the Google Add-On Smartsheet Merge for Google Docs authenticating. I have read the following document: Smartsheet Merge add-on for Google Docs | Smartsheet Learning Center. As well as other articles in the Smartsheet Community and Google search and help results.
After I click Connect to Smartsheet in the panel to the right, enter my Smartsheet account credentials, and click Allow, the page reloads to a Google Drive error message. The panel on the original tab reloads to the same Connect to Smartsheet prompt from when I started.
I have tried:
Clearing all browsing data from all time. Signing out of all accounts. Closing all browser windows. Restarting the computer.
I am using the latest version of Google Chrome and no third-party extensions are enabled. I have verified Chrome is an allowed app in my Windows Defender Firewall.
The add-on shows up in both account settings after attempting to connect, the Google account and the Smartsheet account. I have tried revoking the connection in both accounts and then starting a fresh login with no browsing data or login history.
This add-on has worked and is currently being used by my company. I am trying to set up a new user. My own Google and Smartsheet accounts are working with this add-on, as are several of my coworkers who utilize it as well. Nothing on our Smartsheet account has changed.
On the Google side, we have moved the domain where we send/receive email from Google to Microsoft. We did this back in May but retained a handful of Google accounts to be able to keep the function of this add-on. We have all continued to use it for months after this change.
I tried connecting a free Google account to Smartsheet and received the same error. Before attempting this, I performed the same ritual of clearing and deleting everything for a fresh login on a fresh reboot.
The error is rather cryptic, I can't tell where or what is failing so that we can figure out our next steps. The domain change seems to be the obvious culprit, but then why do our accounts still work, and why doesn't a free account work?
Any insight or experience that might help us find a workaround is most appreciated.