How does the top of the machine snap shut? Is it supposed to snap shut before sealing? How do I seal the bottom of the plastic sheets so that I can seal the rest of the plastic sheet?

Sounds to me as if your seal is no longer sealing. To check to see if your freezer's seal is still working. Get a sheet of paper and shut it in the door. Start at the top and work your way around... yep, even the bottom. pull on the sheet, if it comes out... you replace the seal.

I recently purchased a 2008 BT50 dual cab then 2 days later we had 500mm of rain and of course it leaked :( I had about 80mm of water on the drivers side floor and 30mm on the passenger side floor. I stripped the interior out of the car and started hosing the outside and watching where it was coming in. I took all the windscreen surrounds off and the cowl panel off below the screen there was no water coming in from that area. I had taken the gutter seals off but left the door seals on so the water was running down around the outside of the seals (with the door shut) and out at the bottom. From inside near the drivers side kick panel I could see water coming through seams in the metal work and when I took the door seal rubber off the body on the car I could see water was getting in at the top of the door seal rubber going down the front inside edge of the rubber and getting in through the seam where the rubber push's onto the body of the car (first problem). I took all the door seal rubbers off and run a bead of non corrosive silicon inside the cavity and pushed them back on. It seemed to have fixed the problem I dried the carpet and put it back together..Two weeks later we got another 325mm of rain and it leaked again :( not near as bad this time. Looking at the bottom of the door where the door trim meets the door I could see water coming from behind the trim and then into the car. I took the door trims off and could see water gets in when the window is up (all cars do) and is supposed to run out the drain holes in the bottom of the door but the water was dripping and splashing up to the back side of the door trim against the sheet of plastic that is supposed to seal against the door with the black mastic (it doesn't) and running straight into the car. I cut some plastic and siliconed them onto each opening on the inside of the door frame and then put the factory piece of plastic on as well (properley this time) as a backup.
So far so good.

Hi
There is a seal on top of the machine under the water tank. To get to it, remove the water tank, and set aside. There is a large doughnut shaped cap on top of the machine. Slip a screwdriver on the outside edge of the cap and pry up gently. When it snaps up, go to the other side of the cap and do the same. There is a black seal in the center and if you stick your finger in the center and it lifts out, it need to be replaced. Clean any residue inside the opening with a Q-tip.
When you get the new seal, it won?t slip in. Insert it at a slight angle (double lips down), then take your finger nail and run it around the bottom edge of the seal until it slips in, then push down. Snap the cap back on and your set to go.

Hi There is a seal on top of the machine under the water tank. To get to it, remove the water tank, and set aside. There is a large doughnut shaped cap on top of the machine where the water tank was. Slip a screwdriver on the outside edge of the cap and pry up gently. When it snaps up, go to the other side of the cap and do the same. There is a black seal in the center and if you stick your finger in the center and it lifts out, it need to be replaced. Clean any residue inside the opening with a Q-tip. When you get the new seal, it won’t slip in. Insert it at a slight angle (double lips down), then take your finger nail and run it around the bottom edge of the seal until it slips in, then push down. Snap the cap back on and your set to go.

The cotton bag wraps around the hepa filter - the blue plastic part will not be visible once the bag is in place. The silver ring sits inside the cotton bag to hold the sides of the bag against the sides of the vacuum top-half. DON'T pull the plastic inner seal and outer seal apart. They snap together and snap onto the lip of the vacuum top-half. It's a bit of a struggle snapping the seal back onto the lip.

Hi

There is a seal on top of the machine under the water tank. To get to it, remove the water tank, and set aside. There is a large doughnut shaped cap on top of the machine. Slip a screwdriver on the outside edge of the cap and pry up gently. When it snaps up, go to the other side of the cap and do the same. There is a black seal in the center and if you stick your finger in the center and it lifts out, it need to be replaced. Clean any residue inside the opening with a Q-tip.
When you get the new seal, it won’t slip in. Insert it at a slight angle (double lips down), then take your finger nail and run it around the bottom edge of the seal until it slips in, then push down. Snap the cap back on and your set to go.

I fixed my problem by repositioning the tunnel that is on the front of the pick-up tank. It had moved out of position and not allowing a tight seal. It is the white plastic piece that slides a little bit. Good luck.

Hi
If there is water on top of the machine when you remove the water tank, this is whats happening.
There is a seal on top of the machine under the water tank. To get to it, remove the water tank, and set aside. There is a large doughnut shaped cap on top of the machine. Slip a screwdriver on the outside edge of the cap and pry up gently. When it snaps up, go to the other side of the cap and do the same. There is a black seal in the center and if you stick your finger in the center and it lifts out it need to be replaced. Clean any residue inside the opening with a Q-tip.
When you get the new seal, it won’t slip in. Insert it at a slight angle (double lips down), then take your finger nail and run it around the bottom edge of the seal until it slips in, then push down. Snap the cap back on and your set to go.

You need to clean the jets on the machine arm with an old toothbrush etc... then clean out the debris filter on the bottom of the tub near the dryer bar. The calcification in the little jet areas causes this problem. This should help.

could be the cause. check by putting a slip of paper between seal and cabinet and with door shut, check paper is gripped all round the door. if it is not, try warming the seal with a hairdryer in the faulty place and pulling the seal out gently. many of these seals are foamed in and impossible or v dificult to replace. check also that the hinges are not worn