Server not available. 500:Could not find matching provider (wrong URL)

Hi,

i just installed Ubooquity on docker on my Synology Nas.

In the browser everything works fine, but I cant't access Ubooquity via OPDS. I tried Moon + and Kuboo on android.

Both say "500: Could not find matching provider (wrong URL)

I allready turned on "Enable OPDS feed" in the settings.

What did I do wrong?

Thanks in advance!