Many Android device manufacturers extend the perceived battery life of their devices by aggressively closing apps that run in the background. This can happen with the Proton VPN app, causing your VPN to disconnect from our servers.
To prevent this:
1. Open the Settings app and go to Apps → Proton VPN.
2. Tap Battery.
3. Select Unrestricted.
The Proton VPN will now not be killed as it runs in the background.