I am unable to login grafana deshboard

From the same username and password i am able to login on grafana website but with same uid and password on grafana deshboard it always shows that “Invalid username or password”… in the grafana server Logs it shows the same that “Invalid username or password”.
Then i tries to “Forget password” and on the web deshboard it shows "Email sent but in grafana server logs it shows “User not found”. please help me with this problem as soon as possible.

Thanks in advanced