UR28m: no stand alone for in 1-2?

Hi!
i have 2 synthesizers on inputs 1 and 2.
I am able to hear them and record in my DAW but i hear nothing on stand alone mode.

*I use Jacks
*the gain knob does nothing on stand alone and overdrives when daw is on.

any ideas?

Not a clue.
I mean that literally. Perhaps if you were to provide a few.
I can only advise you read over the operation manual (again?) it seems you haven’t set it up properly.