@Phill C Thanks for posting in our Q&A.
For this issue, how long did the app stuck on downloading and is there any error message? In our official article, it describes how to troubleshoot Microsoft 365 app installation.
https://learn.microsoft.com/en-us/mem/intune/apps/apps-add-office365#troubleshooting
If there is anything update, feel free to let us know.
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