I have deployed Rocket.Chat on my cloud server and downloaded the mobile app on my phone. My phone model is Xiaomi 15, running on Android, and the app was downloaded from the Google Play Store. I have granted all necessary permissions to the app on my phone. In the workspace settings, I have enabled push notifications for the mobile app (this option is enabled by default).

After testing, I found that the deployed service works smoothly during real-time conversations, both on mobile and desktop. However, when I minimize the app to the background or lock my phone, the mobile client does not notify me of new messages. When I reopen the app, it shows "Connecting..." and then refreshes to display the new messages.

Later, I tested the app on an iPad and an iPhone. The results showed that, although there was some delay (no more than a minute), the iOS devices could receive new messages and display notifications normally when locked or running in the background. Therefore, the issue is that Android devices do not receive new messages or show notifications when the screen is locked or the app is in the background.

I initially suspected that the network environment might be preventing proper communication with Google services. However, since the official push gateway is used and other services on the server do not have this issue, this possibility seems unlikely.