The Rytm delay can definitely be heard if you want it to be heard, but it can be subtle and maybe that’s what you’re hearing.
So for an audible delay, you want to set the VOL level on the delay settings page up high. This is the level of the returned signal. Set it to full to begin with - you can tweak it later to get the exact sound you want.
Then you need to set the Delay Send value for the appropriate track. Select the track and go to the Amp menu (page A-4 in the manual). The DEL slider sets how much of the track sound is sent to the delay channel. So a low setting here will still result in a quiet delay signal, regardless of the VOL setting from above. Just turn up the DEL amount until you get a decent level - about halfway up you should certainly be hearing it.
And you’ll also want to tweak the feedback (FDB) setting back on the delay setting page to set how often the sound repeats - a low setting there might make you think nothing is happening (ditto the TIM setting, which determines the bap between the original sound and the delay).
Finally you can get some extra oomph by putting the delay signal through the analog effects. By default this is on (so the delay does go through the distortion and compression), but you might have either turned it off or picked a patch where it’s off. To make sure it’s on, go to the Distortion settings page (B-3 in the manual) and set DEL to PRE.
While you’re there, you can then fiddle with the DOV (delay overdrive) setting, which should solve all your inaudible delay problems forever - unless it deafens you, which will make them worse, if anything.
Hope that’s of some use. Apologies if a lot of it is stuff you already know - it’s hard to tell exactly why you’re having this problem, so it’s best to cover all bases.