I believe the OnIgnite output is your problem. It is the counterpart to the Ignite input, which is not pyro fire in TF2, is it base Source/HL2 fire. If you send an Ignite to yourself ingame you will see it is different and broken.
If OnIgnite does actually work with TF2 fire and that isn't the issue, I have a couple more ideas:
What commands? Some commands cannot be executed via a p_cc to prevent malicious activity.
You are firing from a case, have you verified that the AddOutput is properly being sent to the player entity? Certain entities do not handle !activator properly and there may be an issue in your logic chain.