Phoscon app does not find the lamps/switches etc. that have been set up

Hello
I use the ConBee on the Raspi. I updated to the current stable version a few weeks ago. Now, even before, the following problems occur. Depending on whether I call up the Phoscon app from a browser in Windows 10, on two Android tablets, or from the Android smartphone, I see different views.
On the Windows system I see all lamps, the gateway is (of course) connected, the latest version is displayed.

On the smartphone I see no lights, when I click on Gateway I see…nothing, the page remains empty.
If I enter the IP address instead of the address Phoscon App, it also works on the smartphone.

On an Android tablet with LineageOS it works immediately, on another with STOCK-ROM I can’t get to the working interface with either the IP address or the address Phooscon.de/App.

On all 4 devices it worked without problems 2 months ago.

Now, of course, I don’t want a crystal ball explanation, but rather tips on how I can track down these various different phenomena.

On Windows, I use Firefox, on android, I use chrome and more often lightning.

What would be the best thing to do to isolate the problems?

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Hello, so it work if you use the local ip and not using the phoscon redirection ?
You can try this link and all machine and compare the IP https://phoscon.de/discover

But some days ago the phoscon.de link was totally not working, but only on some users, and during only 24h, and not reproductible, …