Fisher and Paykel dryer not drying
I've had this problem for 3+ years. There are possibly multiple reasons why your dryer trips the reset switch. My dryer has a design issue with the lint trap, in that it allows lint to build up around what I assume is the heat sensor / thermal switch. It's simple, the temperature is detected as too high in the dryer and trips the switch which cuts power to the heating element. The reset switch access as mentioned in other posts requires either tipping the dryer back or removing the front panel, at least partially, to access the switch. After the reset switch is pushed, you'll need to check if there's lint built up that's causing the reset issue. First, find the reset switch.
To access the switch, there are 4 Phillips head screws that need to be removed. For the first 2, lift the dryer lid and you'll see two half-moon shaped rubber inserts at each of the front corners of the machine. The inserts can be pulled out with your fingers or use a screwdriver, gently. There is 1 screw under each insert that needs to be removed. Once those screws are out, you can put the lid down and lift the plastic top of the dryer that the lid normally rests on. It's attached on the back of the dryer so don't worry, it won't come off...it will lift just like the dryer lid. Be careful of the sharp sheet metal edges. Now there are 2 smaller screws, 1 at each front corner, that attach the sheet metal pieces. Remove each of those screws. To get the front off requires a bit of finesse. You'll see that the front sheet metal panel of the dryer has bends in it to attach it to the sides of the dryer. Gently pull at the top corners, one at a time, to separate the front panel from the rest of the dryer. You'll see that there are u-shaped orange or red plastic pieces inserted into the sheet metal sides that align with holes in the front panel to hold the skin of the dryer together...the front should just pull away from those u-shaped pieces. There is a wire with a clip attached to the bottom of the front panel, probably a ground wire...if it pulls off when you remove the front panel, just reattach it when you put everything back together. The front sheet metal is also integral to the front feet of the dryer, so tilt the top of the front panel toward you and lift. The front panel should pull away. When you put the front back on the dryer, do it feet first by aligning the plastic foot pieces, then align the u-shaped side pieces, then worry about the top corners wrapping back around so the front fits flush.
The reset switch is in front at the bottom right of center and is probably orange. Just push it and you'll hear it click. I would vacuum out the lower part of the dryer at the point, but it's probably not what's causing your problem. I've gotten to the point where I use a yard stick or vacuum extension to push the switch without completely removing the front panel. Then I don't have to detach / reattach the ground wire. You'll see after you do it 3 or 4 times!
Now check to see if lint build up is causing your thermal switch to trip. Pull out the lint trap and you'll see 1 Phillips head screw behind where the lint trap normally sits. Remove the screw, and you'll feel the circular plastic piece the lint trap sits in become loose...pull this round piece out of the dryer from the bottom. If there is a lot of lint behind this circular plastic piece, that's probably what's tripping the heat sensor. Vac it out. Gently feel around the circumference of where you removed the piece to see if the fine mesh lint screen has any holes (if it does, it may be blowing lint into your exhaust and eventually clog the vent to the outside). If the mesh is torn, I assume that larger circular piece needs to be replaced at some point in whole or part. From what I can see, the design of the lint filter and trap is ....****. The system allows lint to enter the area where the heat sensor sits.
The short term fix is to vac out the sensor area regularly and that will keep the switch from tripping, if that is your actual problem. I believe F&P is aware of this issue and will probably remedy it for you. I called them once when this issue originally happened and had to wait for a tech to come out do what I described above. I haven't called them since, but have seen other posts regarding a new part or parts that F&P will provide...hopefully free! Good luck!