I was also facing the same problem. But I realised I was trying to push my one git project material on other remote git project. Solution:
Clone the fresh project again and this time make sure cloning link is starting from ssh if you have added the SSH key and https:// if you have added the puttyKey.
Managed by avoiding creating the repository with a Readme.
1. crete without readme.md
2. the 'create-react-app' command already have a 'Readme.md' file.
3. Modify teh readme.md later on.