G'morning Rokins and welcome to the forums!

your other character might not fire if it has not received the target yet or it is still targeting a dead target.
there is a bit of latency between selecting, hitting assist (if you are using this step) and your alts getting the information.
if you hit the '2' numerous times, does it start firing a second or so later? (if so... definite network latency)

if this is not the case, please let me know.

Rob