My Cloud automatic backup fails on large camera roll (Android)

I’ve seen a really old answer for this for iOS, but it doesn’t seem to answer it for android, and I don’t see it in other posts.

As the subject says, I installed the My Cloud app, turned on automatic backup for my camera roll, and waited… I saw the upload start, and then after a while it failed. It has been weeks and the upload has not automatically restarted and I don’t see a way force it to restart.

I’d like the existing pics in my camera roll to be backed up, not just the new pics… how can I fix this?
NAS is EX4100, if it matters. Android 9, samsung galaxy s9. app is up-to-date.

@i_says You may want to place this topic in this sub-forum and see if someone can help.

sorry I’m new to these forums. what is the right way to cross-post to another sub-forum?
should I just copy it? I don’t want to change this post’s forum, because I really suspect its a problem with the mycloud mobile app and not the NAS hardware.