I have two instances of WhatsApp on my Note8. When I receive a message on my primary WhatsApp, I get notifications instantly as normal. However, on my dual WhatsApp, I don't get notifications unless I open the app.
Sometimes, I get notifications come in all of a sudden as if the app has come alive and checked, but this is not consistent with the primary app.
I've gone to Settings->Notifications and there is only one 'WhatsApp' app listed and notifications are enabled. However, this cannot be where the issue is as the notifications are fine for the primary app, just not the dual app.
If I go to Settings->Apps, then here I do see both instances listed. And notifications are enabled for both. I've also checked the Mobile data settings for both, and they both have Allow background data usage enabled. I am not using Data saver.
The only thing I've not tried is disabling Optimise battery usage for WhatsApp as this seems to be for both instances of the app, not either. But other than that possibility, I'm stumped. Any ideas welcomed.