I own a FW with an Atwood Helium reefer. There are two things to consider.
1. Atwood had a terrible time with their supplier that provided the electric heating element. They have a very high percentage of failures on this part. The good news is that the refrigerator has a two year warranty, so if this part is defective, you can get it replaced under warranty at an Atwood authorized facility. If the reefer is cooling well on gas, but not electric, you'll need to get it repaired.
2. The temperature setting control on these units is not intuitive. If you haven't already done so, hold the temperature button down for several seconds to set it to the lowest temperature. You'll see that by the indicator lights on the front panel. Five lights indicates the lowest temperature setting.
If you have it set on the lowest temp setting, and it's not cooling properly, you may need to have it looked at. Have you placed a thermometer inside the unit to see what the actual temperature is? Mine typically stays around 35-36 degrees on the lowest setting when the outside temp is in the 90s.
Jim