am not sure your configuration but if Gmail enables your connection to use modern auth then you should update your connection to use it. I suspect the reason you are seeing the issue is that M365 has disabled basic auth protocol for POP/IMAP accounts, Basic Authentication Deprecation in Exchange Online – September 2022 Update - Microsoft Community Hub. If at all possible, I would proceed to get it working with modern auth. Its more secure and you won't have to change again if you address it now. If you need more time you can open a support ticket from the admin portal and support can help you re-enable basic auth but this will only work until January 2023. After January 2023 there will be no more extensions for basic auth.If you have M365 accounts configured in Outlook Desktop as POP/IMAP those will stop working. Outlook Desktop is not being updated to connect to POP/IMAP with modern auth. Outlook Desktop will only support Exchange connections going forward.