Why am I not getting some notifications after using power saving mode?

[Android Central Question]

I've seen this around the forums but not an answer that works. I used power saving mode over the weekend, and when I turned it off the apps did not restart working in the background (particularly messanger and my emails) I have to open the apps too see if I have new messages.

I have cleared my cache, reset the app settings to the original, and made sure the boxes are ticked to work in the background. Android version 8.0.0. Galaxy S7