I wish I could provide some advice here for you, but I don’t have enough experience troubleshooting. I followed the steps in CAB 1L manual and everything worked as expected. I’ll note though that the horn didn’t blow for me either. There seems to be no user feedback at all during those steps.
Wait, maybe I do have one piece of advice. Mine was an eBay purchase, and it arrived in Like New condition as described. But the prior owner must have changed the ENG settings, because I was getting some wonky responses. I did a reset per the manual On each unit, and that did the trick. I just messed up the lash up settings when fooling around with my additional B unit purchase (from the For Sale forum right here I’m happy to say) which prompted the OP.
Maybe try a reset on each unit and start from scratch?