Put used transmission in on 04 Honda pilot now it won't go in to any gears what can be the problem?

Put used transmission in on 04 Honda pilot now it won't go in to any gears what can be the problem? - 1

You put the wrong year tranny in the car. The PCM will not work on just any transmission that bolts up.
You put a junk used tranny in your car.
Did you use the bolts to pull the transmission up to the motor instead of making sure it pushed all the way on by hand? That usually means the torque converter wasn't all the way on the ATF pump and now the pump is trashed.
Did you even take the ATF pan off and clean it out and put new ATF back in?

Hi so that is the age of this car then the high speed idle makes even more sense along with the fact a modern ECU needs to instructed it has a different gearbox. So time to be visiting a honda dealer or simply JUNK it. After all 13 years is well past it's design date of just 8 years.