Ok wow that stinks and is harder to debug because its a laundry list of generalistic suggestions
1. Just verify for sure the users permissions
2. Since its a pattern of a few times and fails and if it does this for everyone, you may need to change the authentication method you are using to get to the data itself as that can break much more quickly than normal in some instances. You may need to change it to use a specific account to always access the data versus allowing it to do by the user.
3. Lame standard stuff Part 78454 lol, verify permissions and licenses. Should it work EVER without the right stuff.. nope, but bugs happen
4. Is your bot setup to use Gen AI? or only your sheet? I am curious if after a bit or based on the question its actually trying to find the data on the Web or other source that they do not have permission too, or a DLP policy exists to block, so turning off general knowledge sometimes resolves this.
Where is the Agent deployed? Teams? M365? etc does it fail the same way in all channels?
If these suggestions help resolve your issue, Please consider Marking the answer as such and also maybe a like.
Thank you!
Sincerely, Michael Gernaey