Thank you for your suggestions. Unfortunately, the downloaded pictures doesn't seem to work. I have tried to send images downloaded to the computer, and they did not go through. (Again, I get an error message and can see that error message on my phone and hit send...)
Excuse my ignorance, but is there an easy way to force a message to be sent as SMS? Or a group to be formed specifically as an SMS group? The Your Phone app or Samsung doesn't have a clear option that I can find.