HI I have my hot tub at 104 but it will only heat up to about 80 degrees. what is my problem

Well the first thing is that it is inflatable and doesn't have the same insulation as a regular hot tub and number 2 keeping in a 65 degree environment on a concrete floor isn't helping either. The heater I'm certain is working but your variables are taking the positives away.

Is it still calling for heat, if it shuts off before set point, David is right.

calcium will stick to heating element 1st and make it less able to heat water , eventually it will consume the entire surface and insulate the water from touching it and warming it and finally overheat it and cause burnout , high calcium (limestone) is usually a condition that occurs when filling via a well or stream , consider getting a load of pre softened water from a municipal water system , there should be a list of haulers in your area that can provide this service

First thing to check would be the filter to make it is clean however if the tub is not getting to 104 degrees as it should you probably have a thermostat problem.

Rod
US Parts Center

if you wire a hot tub on 230v it will take 4-5 hours to reach 104 degrees
Rod @ USPartsCenter.com

A spa wired 230v with a 5.5 kw heater will heat the water 10 104 degrees within about 4-5 hours.


Rod
US Parts Center
888-521-6183

Contact Maryland Hot Tub Repair @ 410-304-2463 or see their web site www.maryland-hottub-pool-spa-repair.com/ they specialize in Jacuzzi Sundance Service.

check to make sure all the jets are open, this can cause a restriction, that makes the tub think its the filter

This is normal with the dream maker spa. The dream maker spas are poorly insulated, and only run 120 volts with a very small heater.
When the unit is first filled, the hot tub will not heat full time either. Most new hot tubs will have freeze protection below 50 degrees F. They will recirculate automatically using the friction and the pumps heat to warm the water above 50 degrees, and then the heating unit will kick on. These hot tubs do not heat while the jets are on high either, so once you are in it using the jets on high, the temperature will start to fall.

Now that you are up to 80 degrees, it should heat up fairly quick however.