Combat macros can never decide what to cast for you. They can not cast X based on if Y is active/on cooldown/etc or not. They can't decide to skip a spell in a sequence if it is not possible to use it.

If you have a reset conditional in a macro {IE reset=whatever} then, you're probably meeting that conditional. Take it out or use another type, such as reset=combat.

Using commas in castsequences has been gone for a while now. You will need to set up round robin casting in your multiboxing program to be able to have one toon cast, then the second and down the line.

The majority of people are now using "steps" or "toggles" which is basically another form of round-robin casting, but rather than it going from toon to toon per press, it goes from a castsequence or single spell per press on every toon.

How this works will depend on what you are using for your multiboxing program.