Issue
Are Heroku customers required to enable MFA along with Salesforce?
Resolution
Yes.
Heroku customers must enable MFA starting February 1, 2022, according to the Salesforce MFA requirement in order to access Salesforce products.
Heroku users must use MFA for every login through the Heroku web user interface, known as Heroku Dashboard, or the Heroku CLI. You can register and manage MFA verification methods for your Heroku account in your account settings. Heroku MFA is available at no extra cost.
If you're a Heroku Enterprise customer and are using SSO, turn on MFA with your SSO provider to ensure that all users meet the MFA requirement. See more info on MFA here.