Device Simulation Framework issue

I'm writing a simulator using DSF and I have the following problem.
No method of DSF objects returns any errors, but when I do HotPlug() the simulted device appears as an unknown device. The device properties show VID=0000&PID=0000 as if the device was physically connected but did not respond to standard requests. In order to find out what causes the issue I tried handling standard requests on EndPoint0. But the handler was never called. It seems like no request reaches the simulator.
I think I'm doing something wrong because the DSF samples from the WDK work correctly, but I can't figure out what exactly is wrong.
Does anyone have experience of such a situation? What should I try to change?