I had this same issue today (never tried drum sequencing before) and my problem was that I didn’t realise I still had to unmute all the steps using the Note Mute button (3) as well as enabling the steps using Inst Select.
In drum mode is there a reason for this behaviour? In effect you have to enable a step twice (unmute it and then switch it on in the Inst Select interface).
Apologies if I am misunderstanding … I love my ZAQ Sequencer by the way