App would not connect to DynDNS URL

[Kobitv]

Hi,
the Android app function properly when I set it up with IP and Port but would give me a "Connection Problem: com.android.volley.ClientError" when I give as apiScraper api url the dynDNS address (which I already tested from the browser and works).
Can somebody suggest why?
cheers

[Kobitv]

It seems the API scraper answer with 80.142.###.### - - [28/Sep/2019 18:39:15] "GET / HTTP/1.1" 400 -

I do not understand why the API would think this is a bad request from the android app, the only thing I changed is that I use DynDNS instead of direct iP (which my ISP change every day so it is not really an option).

PS: the dyndns is configured on the port 8023 and the router forward also.