Linkus App Not Connecting — Troubleshooting Guide

Introduction

If the Linkus mobile app shows "Connection Failed", "Registration Failed", or simply won't connect, use this guide to diagnose and fix the issue.

Step 1 — Check the basics

• Is your phone connected to the internet (mobile data or Wi-Fi)?
• Is the app up to date? Open the App Store (iOS) or Play Store (Android) and check for updates.
• Try closing the app fully and reopening it.

Step 2 — Check if it works on a different network

• If you're on Wi-Fi, switch to mobile data (4G/5G) and try again.
• If you're on mobile data, try a Wi-Fi network.

If Linkus works on one network but not another, the issue is with the network (likely a firewall or router blocking SIP) — not the app or PBX.

Step 3 — Verify credentials

1. In the Linkus app, go to Settings > Account.
2. Check the server address matches your PBX URL (e.g. yourcompany.ukycm.yeastarcloud.com).
3. Check the username (your extension number) and password.

To reset the password:
1. In the PBX admin portal, go to Extension and Trunk > Extension and edit the extension.
2. Under User Information, reset the User Password.
3. In Linkus, update the password under Settings > Account, or scan a new QR code.

Step 4 — Re-scan the QR code

QR codes expire after 1 hour. If the user set up the app a while ago and it's not working now, they may have used an expired code.

1. In the PBX admin portal, go to Extension and Trunk > Extension and edit the extension.
2. Click the Linkus tab.
3. Click Send Email to send a fresh QR code.
4. In the Linkus app, tap the + to add an account (or remove the existing one first) and scan the new QR code.

Step 5 — iOS-specific issues

Not ringing for incoming calls:
- Go to iOS Settings > Linkus > Notifications — ensure Allow Notifications is on.
- Go to iOS Settings > Linkus — ensure Background App Refresh is enabled.
- Ensure the phone is not in silent mode or Do Not Disturb.

App disconnects after a few minutes:
This is often iOS killing background apps. Enable VoIP mode: in Linkus Settings, ensure the connection mode is set to VoIP Push (available in iOS settings for the app).

Step 6 — Android-specific issues

Battery optimisation killing the app:
Many Android manufacturers aggressively kill background apps.
- Go to Android Settings > Battery > App Launch (Huawei/Honor) or Settings > Battery > Battery Optimisation (stock Android).
- Find Linkus and set it to Unmanaged or Allow background activity.

Not receiving calls:
- Ensure Push Notifications are enabled for Linkus in Android Settings.

Network requirements for Linkus

Linkus uses the following ports — ensure they are not blocked on the user's network:
- SIP: TCP/UDP port 5060 (or 5061 for TLS)
- RTP audio: UDP ports 10000–20000
- HTTPS (API): TCP port 443

Corporate Wi-Fi networks sometimes block these. Try mobile data to confirm.

Tips

• Cloud Edition is designed to work through home routers and 4G/5G without any special configuration. If Linkus doesn't work, the problem is almost always network or credentials.
• Contact X2Comms support if the issue persists after these steps — provide the specific error message shown in the app.

Summary

Most Linkus connection issues are caused by incorrect credentials, expired QR codes, or network/firewall restrictions. Try a different network first, then verify credentials, then check app permissions.