I am trying to install these wall heaters, I have a standard 200amp panel and have a sub panel of 60amps which I am powering a small suite with, a double 20amp is hooked to 12/2 then to the heater I installed the heater as the diagram states and it does not work. I have tried every config, and nothing. I then disconnected a baseboard heater which is powered by the 200 amp panel and the heater worked. I am stumped I have power down to the heater connections and it shows 118 to 119 volts the same as what was on the other circuit.
Does anyone have any ideas

Not following your post. You installed a 240 electric base board heater from a 60 amp sub panel.
You disconnected another baseboard heater which is connected to the 200 amp main panel and the new heater began to work. Is that correct?

Just how are you checking voltage? Is the sub panel 240V?

My guess is you are using a 2 pole breaker that is plugged into the panel incorrectly, so that both poles are on the same phase or leg of the panel.

If so, you will measure 120 volts from each wire to ground, but not get 240 volts across both wires.

Any chance you can upload a photo of the new breaker as it sits in place in the panel?