When you enter your email to reset your password, the password reset link isn't working for the instance you are trying to get into.
Make sure you enter your user ID login in the "Email" box when requesting a password rest link. This is not necessarily your email address, but rather the user ID you use to log in to the instance, which is formatted like an email address.
An admin of your Marketo instance can verify your user ID login for you by navigating to Admin > Users & Roles and checking the value in the "Login" column.
Who This Solution Applies To
Customer who have a user ID that is different from their email address