Exchange Server Security Changes for Hybrid Deployments

I've recently run the HCW and received an error related to OAuth. I had GA permission assigned to the account at the time the HCW was run. I've been manually validating OAuth authentication per this MS document: https://learn.microsoft.com/en-us/exchange/configure-oauth-authentication-between-exchange-and-exchange-online-organizations-exchange-2013-help?redirectedfrom=MSDN

The test run from on-prem is successful (after having to manually enable the Intra-org connectors) but I'm receiving the following error when testing from Exchange Online: "A server side error has occurred because of which the operation could not be completed. Please try again after some time. If the problem still persists, please reach out to MS support". I've run the test multiple times over the past couple of days with the same error. I had just renewed the auth certificate in January and receive a message indicating that the current cert is valid when running the upload cert script provided in the article. 

I'm curious if anyone else is having this same issue and if it might be expected behavior or an unintended consequence of the EWS deprecation efforts. I've opened a support case.

UPDATE: I ran the Test-OAuthConnectivity cmdlet again this morning and received this message: Test-OAuthConnectivity: The cmdlet has been disabled due to internal failure. Please email to us at email address removed for privacy reasons or contact Microsoft Support to report this issue.

I guess its a good thing that I already have a support case open...