Using Classic Outlook on Windows for personal email, calendar, and contact management
This issue is now resolved, It took 3 plus hours for users to notice. Solution is below;
"Just in case, if anyone who is still experiencing this issue, please contact your administrator sign into Exchange Admin Centerand negative to organization > add-ins to disable and re-enable “My Template” add-in. After that, you may need to re-start the Outlook client or refresh the browser if you are using Outlook web APP to check the result."