No permission prompt appears
On macOS, check System Settings for a pending network extension approval. On Windows, confirm the client started with administrator rights.
TUN troubleshooting
TUN will not enable or kills connectivity
No permission prompt, route conflicts, broken DNS, or another VPN taking over. Check each cause separately.
Content reviewed · Nov 3, 2026
Who it is for
People who lose all connectivity after enabling TUN, or never see the permission prompt at all.
Before troubleshooting
- The normal system proxy already works
- Note the OS version, client version, and error text
- Close other VPNs and network managers
Troubleshooting steps
- 1
Turn TUN off and confirm the system proxy still connects. If this fails, nothing later matters.
- 2
Check permissions: administrator on Windows, a network extension approval on macOS, VPN permission on Android. No prompt usually means a system policy blocked it.
- 3
Look for route conflicts: another VPN, a virtual adapter, or a Docker bridge can claim the default route.
- 4
Check DNS: with TUN on, lookups go through the core. A bad DNS setup looks like “connects but cannot resolve”.
- 5
Roll back one change at a time and retest. Changing five things at once is not troubleshooting.
Common issues
Only some apps lose connectivity
Those apps may use their own DNS or proxy settings. Inspect their network configuration before relying on TUN to cover them.
Turning TUN off does not restore connectivity
Restart the client, or restart the network service. Stale routes may still be in the table.
Next step
If the client itself will not start, read the startup troubleshooting guide.
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