We are using an internal certificate on our server and I\'ve followed the steps in
https://blogs.msdn.microsoft.com/tfssetup/2016/12/19/error-ssl-certificate-problem-una
This is what I did to resolve the issue.
Download latest GIT from https://git-scm.com/downloads
During installation setup, select Windows Certificate store for SSL.
Go to Program files and copy the latest GIT folder.
Replace the git folder inside the agent/externals with the latest GIT folder.
Restart agent and build again.