Hello again, its more complex than all that, 24v to the main valve terminals is not sufficient.
You need 24v to the pilot terminals as well. Then the ignition control module allows v24v to the main valve (inside the same gas valve as the pilot gas valve) and the burner lights.
The new valve is not a direct replacement for the old valve unless it came with a wiring diagram stating very very explicitly that it was a direct replacement and showed the new wiring configuration in exact detail...
notice the old valve had 6 wires connected and the new one only 4, I have not looked into it any deeper so far.
None of these items are generic, one type does not fit all so to speak... that may very well be the wrong gas valve....
Regarding the technician. Many are quite bright, very smart and capable people.
At least 5 or 10% of the technicians fall into that class... for the other 90% or so, sometimes make errors some of them are entirely incompetent.
So the fact that the tech said he found 24v at the gas valve, without saying which terminals, tells me that its most likely the wrong gas valve you have installed, and also likely wired incorrectly.... or that the ignition control module or flame sensor is bad.
From here, without tests etc its difficult to say.
On this end I am paid only if you rate my work positively, I get half of your deposit in that case, so that I need to make sure that I am not spending hours on question that are either insolveable on line, or that a customer does not rate positively.
Let me know if you would like me to opt out to other of our experts here or if you would like to rate my work so far positively so far and we can go a step or two further.
Training is often needed, that is one of our premium services if you are interested.