If you insert your sim card in another phone does MMS work ?
I ask as this is typically network driven and some network accounts need provisioning for MMS which the network has to perform.
MMS is also typically a chargeable service and only allows a limited file size to be sent which is why I prefer Facebook Messenger , email or whatsapp myself.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "