I’m having trouble getting sound to play from my UR22mkII. Currently, I only have headphones plugged in with no studio monitors. I have a microphone plugged in and the sound of that does play through the headphones. However, I can’t get any sound to play from my pc from any program. I’ve installed the latest firmware. I’ve gone into the sound settings and tried selecting every sound option on there with no luck. My monitor screen is a TV that has built in speakers. When I change the sound options to that, sound does play from the TV. But just can’t get sound from the UR22mkII. Please help me 
Not sure if you figured this out yet so I’ll bump your post but, at the same time I’ll ask you to provide some more detail about your Cubase software (if applicable) and computer operating system so that someone can try to assist.
You didn’t mention if you were using your UR audio interface with a DAW like Cubase and, if so, are they working properly. Also, if using with Cubase, I am wondering if what you want can be fixed by clicking on the Cubase VST Audio System menu option to “Release Driver When Application Is In Background”.
Other than that you say you went into the computer OS sound system and choose the UR as the default audio device… right? Also, I suppose to hear computer sounds through the UR headphone connection I would think that you have to choose the UR “Main Outputs” in your audio setup as the playback source.
Regards 
Same issue here. I can record but not play back. OS X audio device is set to UR22mkII, Cubase Audio Connections for input and output likewise, Cubase Studio Setup configured to use the right driver. Tried with Reaper, same result, which suggests its either the box itself or an OS X setting. Any thoughts, @Prock?
In case this helps someone (newbie) in the future, having the same issue.
I too could not hear any output from the Jamkazam solo sessions recordings I had made.
I had the Mix knob on the UR22mkII turned completely counter clockwise (CCW) , to “input”. Turning the mix knob CW (to the right) towards DAW … and my output from the recording could then be heard.
Trying to get Jamkazam going. My DAW is the free version of Cubase AI installed 10.5.12 build 123 installed in Windows 10 (that will be next.)
I had a similar issue in trying to set up my UR44C with Jamkazam. I found that by going to the dspMicFX UR-C app and clicking on “Loop Back” I was able to hear my inputs and also the sound from applications on my computer. Although I can now hear these things on my headphones I am still getting an error from Jamkazam stating that my device is not connected. I am getting a similar error on both my Mac and Windows 10 machines. I don’t get it as I believe I properly installed the drivers and I am obviously getting sound through the USB cable from the computer. I am not able to play a backing track in a session and can’t even get a solo session to work in Jamkazam. Has anyone been able to successfully use the UR44C with Jamkazam? I’m stuck and I have not been able to get a response from Jamkazam support. Any help would be appreciated. Thanks.