Oh my, you do not know how long I've been struggling with this aswell a few weeks ago, haha, token was always invalid for some reason.

In the end I chose a different route.

I generated my own guid (key) and stored it with the member properties, and send it with the email.

When the user clicks the link in the email, the guid is attached to the URL, so you can verify it on the backend.

Then instead of using the ChangePasswordWithResetAsync method, I did something like this:

//Injected 
 private readonly IPasswordChanger<MemberIdentityUser> _passwordChanger;

//Code
//Check if supplied Guid matches the member being reset
//If so, reset password:

 var changePasswordModel = new ChangingPasswordModel()
        {
            Id = Convert.ToInt32(member.Id),
            NewPassword = model.ConfirmPassword,
            OldPassword = null
        };
  await _passwordChanger.ChangePasswordWithIdentityAsync(changePasswordModel , _memberManager);

And it works!