Dear Holusojay,
Greetings! Thank you for posting to Microsoft Community.
First of all, I came across a related thread that you may need to first check: Office Add-ins error: Cannot connect to catalog - Microsoft Community Hub.
Now, before giving any suggestions, please provide the information below to help us do investigations:
- Can you please take a screenshot of that error message and upload it here.
- What kind of add-in did you deploy from Admin center?
- Does this issue happen when you deploy a specific add-in or all add-ins deployed from Admin center display that error message?
Kindly understand that initial reply may not instantly solve issues, but we can work together and get a solution.
Apologies for the inconveniences caused! Thanks for your cooperation and understanding. Stay safe!
Sincerely,
Edwine | Microsoft Community Moderator.