[SOLVED] YaCy suddenly cannot be reached from outside

SOLUTION: In your VPN controls, request another, randomly allocated port for forwarding and in the “Use Case and Account” settings page, specify the new port. Save the settings and then restart YaCY. In the browser, you will need to enter the new port number after the colon in localhost:
You will need to re-enter your passphrase and username too.

Though this solves the problem, it doesn’t explain why it happens and each time your system reboots you might need to go through the process again.

Earlier, the YaCy instance was running well in senior mode. Though no changes were made, other than a reboot, now YaCy indicates it cannot be reached from outside. This is strange.

The machine connects to the internet via a VPN, and the VPN is port forwarding 8090 OK, it seems.

So what might be the problem?