Since day one, my fold has a problem sending pictures/video/voice recording messages out by using WiFi. I need to switch to my cell data to send these out, then switch back on WiFi. On voice languages are not picking up on with these punctuation that I need to stop and type bottoms to continue messages.
Go into settings
Have default setup set to automatic
Then select automatically so the phone searches for the best network connection.
Reset the fold and it should be working again. I have the unlocked varient if thats useful. If it doesn't work go back where you were in the settings but switch your network mode from 5G to LTE and see if you can send messages that way. Could be a modem problem. Hopefully not.
All else fails under mobile network settings tap on access points
The following screen tap the 3 dots in the upeer corner and tap reset. This'll reset your network apn settings to default and cure your problem. Sorry for this wall of text :)