Error pushing to github using 0.26.2

I'm using 0.26.2 to push files to github, and it gives me request failed with status code 500, and I'm using personal access token of github for authentication.

following is how I create push option
return new PushOptions()
{
CredentialsProvider = CreateCredentialsProvider(),
OnPushStatusError = new PushStatusErrorHandler(error =>
{
throw new NonFastForwardException($"{error.Message} at {error.Reference}");
})
};

and following is how I create Credentials Provider:
return new CredentialsHandler((url, userNameFromUrl, types) =>
{
return new UsernamePasswordCredentials()
{
Username = credential.UserName,
Password = credential.Password ?? string.Empty,
};
});

can somebody help me to find out what's wrong

No file or test is named. Start by reproducing the push with libgit2sharp 0.26.2 and the shown PushOptions and CredentialsHandler, then inspect the complete failure details and authentication behavior. Done means identifying a reproducible cause and documenting or verifying a fix for the HTTP 500 response.