Moved this from Community Interface Help to Business > ePO for better support, good luck.
Most likely the domain admin account is being used by ePO to log in to SQL - now that the password has changed, ePO can't access the database any more.
You need to update ePO with the new password: on the ePO server, go to
and log in with an ePO global admin's credentials. You will then be able to enter the new domain username and password: please make sure that you check that the credentials are correct by using the Test button before you click OK to confirm the changes. After you click OK you'll need to restart the three ePO services for the change to take effect.