Is there anything that would cause a digital phone on BCM 50 3.0 to make speakerphone capability unavailable?

I'm to see a customer tomorrow who claims that one phone is always on 'mute' they have to lift the handset to talk.

Probably a defective phone maybe, but I wanted to ask if it could be programming... ?

Definitely could be programming.

Usual issue is handset is plugged into headset port. This will disable the speakerphone.

Both answers above are correct.

Once you check where the handset is plugged into (should not be the middle plug) then do a Feature *0 and push the bottom right button on the phone. Does the display say "Handsfree/Mute" ?