Hi litterhodey,
Welcome to the Heartland Owners Forum and Family. We have a great bunch of people here with lots of information and all willing to share their knowledge if needed.
There are several reasons you may not get hot water... do you have propane and is it turned on (switch on the panel for tank levels must be on also) ?? Is your battery hooked up and charged?? If your trying the 120v you still need 12v and on most of the units there is a little switch on the outside of the water heater that you may need to turn on along with the switch inside.
Also, if the water heater is on and your getting warm water,,, the heater may be in the bypass mode...
Now,, I am wondering if you did not try it during the PDI??? That is what a PDI is for,,,, check it all out and make sure it works.
Let us know what the out come is...
Jim M