Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi Shron4222,
Thanks for your quick reply.
From your feedback, I checked on my side and I here didn't have Thunderbird application. For your current situation, if your organization set up single sign-in(SSO) authentication method, then it couldn't support for this application. Please refer to the article to check if app properties is correct:
https://docs.microsoft.com/en-us/azure/active-directory/manage-apps/add-application-portal-configure
Besides, based on the steps and screenshot you provided, my thought is the same to yours, which the setup was finished. It may needs some settings or change about Thunderbird. Since the Thunderbird is third-party application and we aren't familiar with it, we also suggest you contact their support and post your current situation to get further and more efficient assistance.
If you have anything unclear, please feel free to let us know.
Regards,
Joey