Prompting for account when trying to open Excel with Power BI data

Hi, Zenna121 

Based on your description, every time a user works with an Excel document in a Power BI environment they will keep being prompted to log in to their account, this could be due to the following reasons:
1. Although you mentioned configuring SSO, changes to back-end security policies or updates to Power BI or Office 365 may sometimes require re-authentication for security reasons.

2. Credentials have changed or expired: If a user's credentials have recently changed or expired, Excel may prompt the selection of an account to refresh the access token.

3. Power BI features require a Power BI Pro license. If the necessary license is not detected, Excel will prompt you to select the account to log in using the account with the appropriate license.

You can try the following options to resolve this problem:
1. Check account permissions to ensure that your colleague's account has the required permissions to access Power BI content linked from Excel.
2. Make sure your colleague has a valid Power BI Pro license.
3. Update both Excel and Power BI to the latest version.

Best Regards,
Yang
Community Support Team

If there is any post helps, then please consider Accept it as the solution to help the other members find it more quickly.
If I misunderstand your needs or you still have problems on it, please feel free to let us know. Thanks a lot!

How to get your questions answered quickly --  How to provide sample data in the Power BI Forum