MMS & Verizon Message +

I know some of you may not believe this, but up until a few months ago I was able to send/receive MMS (photos and group conversations) using my native text app on Galaxy S9 WITHOUT using either wifi or mobile data. Something changed then (I think a Samsung update) and the native text app no longer allowed this. I switched to Verizon Message + and, bingo, I could return to MMS usage WITHOUT using either wifi or mobile data. This worked until a couple of days ago when another Samsung update occurred (I think Android 10). Now Verizon Message + won't work, so I have to use either wifi or mobile data for MMS usage. Can anyone shed some light on this issue?