“The app does not ring” and “calls do not arrive when my phone is locked” are the same problem with one cause: push notifications.
How the app actually works
The 3CX app does not stay connected in the background — if it did, your battery would drain in hours. Instead the system sends a push notification to wake the app the moment a call arrives. If that notification is blocked, the phone stays silent even though the system is working perfectly.
This is why the app often rings while you are looking at it, and stays quiet once the screen locks.
Check these in order
- Notifications are allowed. Phone Settings → Apps → 3CX → Notifications. Everything enabled, including sound and lock-screen display.
- Battery optimisation is off for 3CX. This is the most common cause on Android. Set 3CX to Unrestricted in battery settings. On Samsung and Xiaomi devices also remove 3CX from any “sleeping apps” or “battery saver” list — these are separate from the standard Android setting and are added silently by the manufacturer.
- Do Not Disturb. Check both the phone’s DND and the status set inside the 3CX app itself — they are independent. An extension left on “Away” or “Do Not Disturb” will not ring.
- Focus modes (iPhone). A Focus schedule can silence the app on a timetable you have forgotten about.
- You are logged in on another device. If the same extension is answered on a desk phone or the web client, the mobile may stop alerting.
Still silent?
Sign out of the app and sign in again. This re-registers the device for push notifications and resolves most remaining cases — particularly after an operating-system upgrade, which can invalidate the old push token.
When to contact us
If the app still does not ring after re-registering, or if it affects several users at once, open a ticket. Tell us the extension number, the phone model and its operating system, and the time of a call that was missed.
Support is available 24/7: info@its.ae or +971 4 378 2255.