Diegaiso, try this:
In Security APP (include in Flyme OS):
Permissions; Notification Management -> Google Services: ON (only verify, is normal status, I think)
Permissions: Autorun Management -> Google Services: ON (only verify, is normal status, I think)
Power: App Management -> Google Services: ON (very important, I think)
Afer this, install app from Google Play called PNF No-root (search Push Notifications Fixer). It’s free.
And that is all!!. In my case, working since version 4.5.7A from actually version in my case (Flyme 22.214.171.124 beta). Push notifications in Whatsapp, mail’s app’s (meizu, mailwise,…) is working perfectly,…
Note: Idea partially extracted from the support pages of Whatsapp. In this page, reference to another application (DNSet) that I did not need to be installed but you can use it if does not solve your problem becomes.
I hope you help,…