Hi David,
Be sure you have more administrator licenses available. That's the reason why you can't change the role to 'Administrator' or 'Password Administrator'. You can check that from your profile button in PMP (where you see the'logout' option) and click on 'License'. There you will see 'Number of Administrators'. If you have reached the maximum of Administrators, you can't enable other user to be 'Administrator' or 'PAssword Administrator' in PMP.
Regards from Mexico.