3rd-party notifications not coming through

Ever since a few days ago, I have not had any notifications from apps other than built-in ones coming through my device. I did not change any settings (I did do a software update, but I did that after the problem arose, and the update did not fix the problem). I reviewed all of my settings, and then ended up resetting all settings, and even went as far as wiping the phone clean and restoring it through a backup. After restoring through the backup last night, 3rd-party notifications came back briefly, but between then and now they aren't coming again. Anything I'm doing wrong, or something that can help with this? I feel like I've done all the options.

I really need your help!