Hi @Yiannis Kotzias | Phaedrus Living
I find you add an "Office Mac" tag for your thread, are you inserting comment in Word documents or other Office files that stored on SharePoint? Any misunderstandings, welcome to let me know.
Please go to Outlook for Mac > File > Office Account
, sign out your work or school account, and then restart it to sign in account back.
If it does not work, I suggest you update Office for Mac for a test.
Besides, please also check whether this issue occur with Office for web, check whether this issue occur with all Office files stored on SharePoint or OneDrive for Business.
Any updates, welcome to post back.
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