[git] Authentication failed for https://xxx.visualstudio.com/DefaultCollection/_git/project

I suddenly started receiving this error when attempting to push changes from VS2017 to a VSTS Git repository. This functionality had worked the day before.

I checked my git.log file and saw a different exception :-

19:43:57.116665 ...zureAuthority.cs:184 trace: [ValidateCredentials] server returned: 'Unable to connect to the remote server.

I downloaded the latest Git CredentialManager source from Gits Credential Manager repo and debugged it.

Once authenticated, the following exception occurred :-

No connection could be made because the target machine actively refused it 127.0.0.1:8888

I then realised that I had recently setup Fiddler to act as a proxy for all services as per the article capturing-traffic-from-.net-services-with-fiddler

Once I ran Fiddler, I was able to successfully connect.