Why is 'Maintain Memorized Payees' always grayed out? Cannot access this feature
The functions in "Maintain Memorized Payees" only activate if there is at least one fix action to be taken. So, "(no items)" text in the message … no actions to take … you have a good MPL.
Is there anything going on in your MPL that concerns you?
For example, in Edit / Preferences / Data Entry and Quickfill, is your setting "Remove memorized payees not used in [xx] months" enabled with a checkmark and is [xx] set to 12 or greater? That's about the only routine housekeeping that one should have active for the MPL.