Also kindly check that the notification settings are all enabled
On Oneplus in your home screen
- Long press on the 3CX icon
- Tap on the (i) icon
- Tap on Manage notifications
- Make sure that under Categories, incoming calls and Missed calls are enabled
Also make sure that the required permissions are granted
On Oneplus in your home screen
- Long press on the 3CX icon
- Tap on the (i) icon
- Tap on Permissions
- Make sure that Phone, Notifications and Microphone are enabled
If the above are correctly set, does the "Keep active' mode help with resolving the issue?
- “Android App Settings (top left hamburger menu)
- Tap on Keep Active
- Tap on OK
- Try reproducing the issue