Why can't I play videos saved in Google Photos with Data once they're are removed from my device?

[Android Central Question]

I take videos with my android lg g4 and it automatically uploads to my google photos acct. I then delete those vids from my phone. Those vids will play when I'm at home with wifi & when I turn wifi off & use Data (w/ only 1 of 5 bars). But once I'm out in the field using only data (with 4 of 5 bars), the vids fail to play, displaying "Can't play video". To try to fix, I uninstalled & re-installed google photos app & cleaned system cache, and run AV, but it's still a persistent issue. Upon reading, it seems to be related to the vids having been deleted from my device, but I don't get that, as that's why people upload them to google's cloud...so you can free up your phn memory. I suspect I have a wrong setting somewhere but can't figure it out. If anyone can help, thanks in advance!

 

[B. Diddy]

Welcome to Android Central! You don't have Restrict Background Data turned on in Settings>Data Usage, do you?