No AirPlay mirroring

Losing my mind here.

Had a 17,1 iMac running on Monterey nicely with OCLP, AirPlay mirroring working.

I upgraded to Sequoia and patched it up. Literally everything works apart from AirPlay mirroring!

I've repatched, reinstalled (always checking that Feature Unlock is enabled) and nothing works.

Everything else seems to be fine.

Any tips?