I initially thought I wasn't receiving notifications because of an issue with 'Do Not Disturb', but going into settings --> accounts --> Google, I realised my Gmail wasn't syncing. Turning sync off then on again pushed my notifications through, but then I have the same problem whenever I receive another email. I'm having similar issues with Outlook, WhatsApp, and basically every single app. I need to have the apps open in the foreground for them to receive any messages. I've tried turning 'adaptive battery' off, but it just turns itself back on as soon as I close the menu. Help?