Konrad, I don't know how you can reproduce this error. I was running Jamulus 3.4.5 and that worked fine. I removed it and installed Jamulus 3.5.0 and from that moment the error appeared. I have an old Mac with High Sierra 10.13.6
When I start Jamulus server on my Mac the following message appears: Execution of PAC script at "http://wpad/wpad.dat" failed: The operation cannot be completed. (NSURLErrorDomain fout -1003.) How can I solve this problem?