Can't download MMS messages on Galaxy S7

This happens occasionally.  Enough that it is annoying, but not enough to knock me out of business!

I occasionally get a text message that says, "No subject//Message size ??KB//Expires hh:mm, mmm dd"  There is a download arrow to the left of the message.  I'm assuming that the messages in question are videos.  The most recent one was 32KB and expires at 23:15 Feb 17. 

Most videos/pictures download automatically.  No changes have been made to settings that I can recall.  Every time I've gotten a text like this, I tap the message and a "wait" symbol appears seemingly indicating that the file is being downloaded.  However, nothing ever happens.  The "wait" symbol eventually disappears and changes back to a download arrow.  No picture or video shows up within the message space.  I've checked "MyFiles" and do not see that anything new is in the "Downloads" folder.  Sometimes I get a message that says "Failed to retrieve".

In the most recent case, Wi-Fi was on (I was home, it was after bed time, and I turn it on so that the phone backs up.) BUT, cellular data was on as well.  I looked back and found a larger file that HAD downloaded, so it doesn't seem to be file size related.

Is this just something that occasionally happens, or is there something I can change that will prevent this?  I wouldn't mind if it didn't automatically download IF I was able to download it after the fact!  Incidentally, I have tried to download with Wi-Fi off since the original failure.