The F04 error on your dryer means that the drying time has exceeded the programmed time for that cycle. What that means is the dryer is not heating or drying well.
The most likely thing causing this error is a restricted vent or bad blower. I recommend you first remove the vent hose from the back of the dryer and run a medium load with the vent off and see if it dries any better.
There are two sensor bars located inside the dryer drum in the front on the lint cover. These can be cleaned with rubbing alcohol. Fabric softener can build up on the sensors and give a false reading to the control and cleaning them may help with this problem.
If the vent is not restricted and the sensor bars are clean then a reoccurring F04 error can be caused by a fault in the main control.
I hope this information is helpful resolving your problem but if you have any additional questions, additional details will be needed.