I had the same issue and tried all the solutions which I knew, and neither of them worked actually after long research I found the solution for the error as below:
The problem with your branch is that you are not tracking your files locally but the identical files are getting tracked remotely so in order to be able to "pull" the system need to be forced to overwrite your local files which are not the version controlled.
So try running below commands :
git add *
After executing all above commands it will track all your files and remove all of your local changes to those files and after that it will get the files from your server.