I noticed after updating to 18.1 that I too wasn't receiving push notifications and tried all the remedies that have been suggested and nothing fixed it. In the end I actually erased my phone and set up as new, didn't use a back up to set it up and although its been long and tedious re-installing all my apps, I have noticed that push notifications have begun working again.
However, there are some apps where the notifications just aren't working, and the ones that are seem to have quite a delay before receiving them.
It's actually not just push notifications I'm noticing this on, when you have to send a code to your phone via text to authenticate yourself for different sites etc, I'm noticing quite a delay in receiving those texts as well.
Very frustrating and I hope it's fixed in 18.2 as well as the touch screen responsiveness. I'm still having issues with that bug.