For the security of your account and personal data, MyHeritage requires passwords to be updated periodically. If your password has not been changed for an extended period of time, it will expire automatically and you will need to create a new one before logging in again.
This is a standard security measure designed to keep your account and data safe.
What do I need to do?
You will need to set a new password. For step-by-step instructions, see: How can I change my password?