Does one volt really matter on an input rating?

I am not sure if it will matter here.

I can say, one volt will cause more current to travel through the circuit than it did. One volt the other way will cause less current to travel through the entire circuit. If you have components that require a specific current before they go into a mode of operation, you would never reach that point with one volt less.

If you have sensitive components that will heat up too much if there is one volt too much - they will fail ... that will destroy themself.

I would say one volt matters in most circuits, but in this circuit if there are no crutial components then it shouldn't matter.....so why is it not working right?

Maybe a continuity test should be done first to ensure noting is fried... before ordering the proper power supply....

BTW - power supplies are pretty cheap these days, you really should just buy the proper one from the start instead of trying to " Make Do" with whatever happens to be laying around. That is how fires are started....

One volt shouldn't matter for a device like this.

With no other information on the controller or your power source, or even what tools you may have available, I can't possibly offer debugging advice.

try an online search for a 19vac