Ceiling light connection timeout issue

I have some troubles connecting my ceiling light to the Yeelight app. Manually it works well, but unable to connect to the app.

I have 4 of them, and only issues with 1.

I see the MAC adress on my phone, than I select the router, after that it gets fastly up to 45%, than fastly to 69%, and after that it goes slowly up to 99% with message “Upadating connections status, just a sec…” and at the end “Connection timed out”.

It has been few months trying to connect it without success. I reset the lamp each time before trying.

Living in Europe, I am connected to german server.
I can see the lamp on my router, but not in the app…

Can you help me?