Mobile Data - Background Apps not working

[Jook]

Hi, I have a Samsung S20 5g phone. When it is on WiFi I have no problems with messaging apps that use data e.g. WhatsApp and Signal. However when using mobile data none of the apps seem to receive any messages until the apps are opened. 

I  have checked the apps are set to use background usage and experimented with the battery optimiser. The phone is up to date.

Could this be a faulty phone or sim? Does anyone have any other suggestions? 

[Jook]

Updating my own problem here incase it helps someone else. I think I have fixed my issue. 

I went to network mode under mobile networks, and changed it from 5g lte to the 3g setting. My notifications seemed to then behave. I switched it back to 5g and it still seems to work. I'll be keeping an eye on mine but perhaps the toggling of the network mode forced a refresh of some corrupted settings. 

[Jook]

Just an update. This is still an issue. Even on the LTE / 3g/2g mode. Seems to work for a while though. I am on the three network. Looking at other threads it seems like their is a problem with the phone? 

[chrismcmath85]

I have the samsung galaxy s20 fe 5g and my data service isn't working while off WiFi and my provider has checked all things on there end and that is working any ideas