ur824 synth output issue

Evening music makers,

my specific problem is that i cannot hear any audio out via my interface for any of my hardware synths, yet i hear my guitars straightaway.

if i plug my guitars into either input sockets one or two, i can hear the audio straightaway, yet any of my synths(ob6,p12,ti2, etc (which i can hear happily output via their own)headphone sockets produce no audio output when plugged into the same input sockets of the ur824.

yes, i have set the hardware synths to midi channel one(just for test purposes), set their track volume to maximum and centered the panning.

apologies for this very basic question but it keeps on thwarting me.

any ideas from guitarists and synth users?
I’ll send you some virtual weiss beer as payment/
thank you very much

It is impossible to say what the problem is with the information you have shared here.

The UR824 does not have any sounds on board. The midi connections are simply there to pass through USB to a virtual instrument on your computer.

If you connect audio out from your synths to the UR824 it will work the same as your guitar.