When you receive a password reset email, the link in the email is only valid for 24 hours (this is to protect your account from fraudulent access). 

If the time has already expired and you weren’t able to reset your password, you should request a new password reset email by going to this link: https://www.tes.com/lessons 
Click on the green LOGIN button in the upper right hand corner. 
Then click the blue link that says "Forgot your password?" found above the Log In button.