There are a few conditions, yes.
It's been a while, but I think the engine has to be warmed up. Did you wire up the vtec pressure switch or just the vtec solenoid? If there are other faults in the engine, vtec may or may not engage also (depending on the cause).

By the way, if you're using a P06, vtec won't engage. It's not a vtec ECU. It's also not a OBD0 ECU, it's OBD1. It's actually the same as P28 ECU but without the vtec parts, so it can be converted if you can get the parts. I used to know where to get them, but I don't remember.

The PS9 is a auto tranny version of the Civ/CRX Si PM6 ECUs. I can convert PM6s to have a vtec output, but I don't know about the PS9 because I've never touched one before. Supposedly they're the same as the PM6s though.

I'm quick, I just got your PM.. lol