This probably means you are NOT using your email address when you try to login after resetting your password.
Make sure you type your email address into the first box, and your password into the second box. Typing your name or some other value, won't work.
When you reset your password, using email or mobile, you get sent a link to change the password, then you are logged in automatically. If you then try to login again, but you use something other than your email address to login (such as a username) that does not actually exist on your account (even though you may believe it does) your login will fail again.
If you have this problem, please ONLY use your email address for login.