Hi @GDR ,
Could you share the template you are currently using?
The first thing to note is that the two connectors, Office 365 outlook and Outlook.com are different.
If the template uses the Office 365 outlook connector, then you need to use an Office 365 account and cannot use an outlook account.
If it need to use the outlook.com connector, both outlook account and office 365 account can be used.
Since your template needs Office 365 outlook connection, you could delete the connection of outlook.com in the connection list, and then re-create the office 365 outlook connection using Office 365 account.
Finally re-use the template to configure Flow, select the created connection.
Please take a try.
Best Regards,