Client cannot find server on QNAP NAS

Roon Core Machine

Roon on QNAP TS-453A for 3 years without any problem.
I have the last stable Rpon package installed.

Networking Gear & Setup Details

Connected Audio Devices

Number of Tracks in Library

Description of Issue

Suddenly, I cannot connect any more to the server from any client, PC Windows 10 and android tablet.

When I try to connect, the connection screen is on forever.

I already reinstalled Roon client on my PC. I already stop and restart the Roon Server running on QNAP.

I did not reinstall server on QNAP because I don’t want to loose my personal data (playinglist etc.).

Please help me…

Thank you.