Hi,
Good day to you and hope you are doing well.
According to your description, the error message appears when you try to connect to a API link in Excel. Sorry for the inconvenience caused at your end.
We'd like to share following suggestions, you may have a try.
1.Try to use the Organization account option to sign in your account.
2.Clear existing permissions:
Go to Data tab> Get Data > Data Source Settings > Global permissions > click the drop down icon on Clear Permission, click Clear All Permissions, Delete.
Then try to connect to API link again.
If the error message persists and you still cannot access the API link in Excel, very sorry about it. We deeply understand it has affected your work.
Very sorry to say that we have limited resource for API related issues, so we're afraid we may not test in same environment as yours to further troubleshoot this issue.
We sincerely suggest you post the question in Microsoft Q&A Community - excel for IT pros where members and experts in that community may have more resource for this kind of situation, they will focus on your question and share specific suggestions based on the specific situation on your side.
Your patience and understanding are highly appreciated.
Hope you are keeping safe and well.
Best regards,
Tina