github recently switched to an https scheme as the default for cloning repos. as a side effect you may suddenly be prompted for a 'Username' and 'Password' when you push where, previously, you were able to do so without typing in credentials. the solution is to cause git to cache https credentials which is easy, since git uses curl under the covers
in your home directory create a file called '.netrc', for example
/Users/ahoward/.netrc
in it put these contents
machine github.com login YOUR_GITHUB_USERNAME password YOUR_GITHUB_PASSWORD
fixed!
First, type the command 'gh auth login' in the command line, then use the arrow keys on your keyboard to select the option 'GitHub.com' and press Enter. After that, choose the 'http' , and then log in to your account through browser.