Solution for this -
Problem -
$ git clone https://github.com/abc/def.git
Cloning into 'def'...
remote: Repository not found.
fatal: repository 'https://github.com/abc/def.git/' not found
Solution - uninstall the credential manager -
abc@DESKTOP-4B77L5B MINGW64 /c/xampp/htdocs
$ git credential-manager uninstall
abc@DESKTOP-4B77L5B MINGW64 /c/xampp/htdocs
$ git credential-manager install
It works....