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

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

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

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