No sound from external fx

Hi. I use Cubase 11.5 with a UR816C.
I’m not sure what I’m doing wrong. I use external instruments with no problems. The send buss is “UR816C Daw Direct 2 & 3” to the rev500. The return buss goes to into 2 available channels in the UR816C.
Is that correct?

Have you set your I/O up for an external effect in Audio Connections?

Yes I have. Perhaps the problem is with the audio interface?
Thanks for your reply