Who I have the same questioned this topic

Within the last month neither my wife or I can send a MMS. We have different phones. My wife has an iPhone X. and I have a Samsung S10. The iPhone can send iMessages with no issues, but if it attempts to send a MMS to a non-iPhone it gets a failed to send. Whenever I try to send any MMS it fails to send.

This is the case whether we are on wi-fi or 4G networks. I verified that MMS messaging is turned on in the phones. The only recent change was we went from the unlimited data plan to 10GB a month. We are no where near our 10GB limit, so this should not affect the MMS.

What can we do to restore MMS messaging?