I have galaxy a8 (2018), whenever I lock my phone, after some time suddenly internet is not working.
I dont get notifications from chat apps etc. and also for example if Im logged in with WhatsApp web, some time after locking my phone, I get no connection error on whatsapp web, when I unlock my phone suddenly i get all the notifications and it recconects to whatsapp.
I know for sure its not just with whatsapp, I dont get any notification from an internet depanded app when the phone is locked.
I checked and data saver is off, notifications are allowed, background activity is allowed, background data usage is allowed, Put app to sleep option disabled in device care, of course do not disturb disabled.
It is also not depanded on WiFi/Mobile data, I mean it happnes on both.
It gets me crazy!!
Model - SM-A530F
Android version 9
One UI version 1
It is up to date.