Is there any chance you can tell us what fixed it for you? We had another report of a similar issue within the same day you posted this, and I’m wondering if there’s a patter here that we should be aware of.
To connect to the visualstudio.com nuget feed Octopus asks for credentials (email / password). When we got the 401 we just entered the credentials matching the one of the e-mail address that was already configured, assuming that user had changed his password. This did not work.
What we had forgotten is that instead of the user’s credentials you must use a Personal Access Token. Maybe some extra help text could be added in Octopus?