My previous supposed fix did not work.
I must have clicked on the wrong personal account. (Sorry)
One of my personal accounts works, the other personal account fails with the BadGateway and "The API version 'V2' has been deprecated.".
The one that is failing is the same account as is running the flows.
So I tried to add the bad account in on a different login's make.powerautomate.com outlook.com connection.
The bad account was unable to be added and fails with the same error.
I have confirmed that the account allows MSFT Power Platform to access it.
MSFT Power Platform has the same permissions on both accounts.
When the app disappeared from the list of approved apps, I then tried to add a connection in make.powerautomate.com.
This pushed me through the consent process, which added MSFT Power Platform back in, but it still failed with BadGateway.
To be clear I can not create a new outlook.com connection for one of my Personal accounts, it fails with BadGateway.
This Personal account was working up until the 28th of November 2024.
I can login to the Personal account and view email via outlook.com.
I have an existing working connection to OneDrive with this Personal account.
It has permissions granted to the MSFT Power Platform to allow access.