Dear Jonnie,
Thanks for posting in Microsoft Community.
According to your description, it looks like you have protected an Excel workbook and uploaded it to Teams, but other users can still add, move, rename and delete sheets in the workbook.
May I know if my understanding of the scenario is right?
If yes, I did a test from my side. Firstly use Excel desktop app to protect a workbook via Review >Protect workbook > set a password. Then I upload the workbook to Files tab in a channel.
When other user in the team open the workbook, it shows the add sheet button(+ button) is grayed out, and if the user right clicks a sheet, it shows most of the options are grayed out.
We understand you want to prevent people from changing workbook structure in Teams.
As we cannot reproduce the issue, we'd like to help you do troubleshooting, could you confirm information below? It will help narrow down the situation.
1.How did you protect the workbook before uploading it to Teams? Did you use the same steps as we mentioned above? If not, could you share with us your detailed steps?
2.If a user right click a sheet in the workbook in Teams, what options do they get? Could you share a screenshot when a user right click the sheet?
3.Does the issue happen to uploaded workbooks in a specific team or different teams in Teams?
Thanks for your patience and understanding!
Hope you have a nice day and stay safe and healthy always.
Sincerely,
Tina | Microsoft Community Moderator