Why am I not notified when I receive a new U Messenger message or incoming call on some Android phones?

Asus Enter Auto-start Manager and enable Allow switch of U Messenger.

Some Android phones have power saving features that block U Messenger's background services, which handle messages being received. To avoid this, you'll need to change some of your phone settings and allow U Messenger to start background services.

Here is how you can change the settings on some specific Android phones:

• XiaoMi
  Step 1: Enter Security Center > Permissions > Autostart and then make sure U Messenger is selected.
  Step 2: Enter Settings > Additional Settings > Battery & Performance > Manage Apps Battery Usage and make sure U Messenger is not in the prohibited list.
  Step 3: Enter Settings > Permissions > Other Permissions > U and then enable the option Show on Lock Screen
  
  
• Sony
  If you enable “STAMINA Mode” in Power Management Setting of your Sony mobile phone, you need to allow U Messenger to run in background under “STAMINA Mode”.
  
  To do this, enter Settings > Power Management > STAMINA Mode > Apps Active in Standby > Add Applications and then adding U Messenger in the list.
   
  
• Asus
  Enter Auto-start Manager and enable Allow switch of U Messenger.
  
  
• Oppo F1
  Step 1: Open U Messenger on your mobile phone.
  Step 2: Enter Settings > Application management to find U Messenger in the Running tab.
  Step 3: Tap the Lock icon and follow the instructions to lock U Messenger.
  Step 4: Enter Security Center > Privacy permissions > App permission management > Floating window management and allow U Messenger work in the floating windows.
  Step 5: Enter Security Center > Privacy permissions > Startup manager and allow U Messenger to startup in the background.
  Step 6: Enter Settings > Battery and storage > Battery manager > Power consumption details > Optimization for excessive power consumption and disable U Messenger in the setting.
  Step 7: If you have enabled Power Saving mode on your mobile device, please continue to enter Settings > Battery and storage > Battery manager > Power saving app control and management and then add U Messenger in the Data Saving app list.
  Step 8: Reboot your mobile device.
  
  

• Oppo A39,F1s,R9s,R9s+
  Step 1: Open U Messenger on your mobile phone.
  Step 2: Enter Security Center > Privacy permissions > Startup manager and allow U Messenger to startup in the background.
  Step 3: Enter Security Center > Floating window management. Find U Messenger and enable it.
  Step 4: Enter Security Center and then tap the button Quick scan to complete the scanning.
  Step 5: After the scanning is complete, enter Security Protection on the same page. Find U Messenger and then tap the button Add to whitelist to add U Messenger to the Whitelist.
  Step 6: Enter Settings > Notification and status bar > Manage notification. Find U Messenger and then tap on it.
  Step 7: In the U Messenger notification settings enable the two options Display on lock screen and Display at the top of the screen.
  Step 8: Enter Settings > Battery. Find U Messenger and then tap on it.
  Step 9: In the U Messenger battery settings, disable the two options Freeze when in background and Automatically optimize when an abnormally is detected.
  Step 10: Go back to the device Home Screen and then tap the physical “Menu button” in the lower left corner.
  Step 11: Continue to U Messenger and then tap the lock button on U Messenger to lock it.