On our jura ena3 we get a message that the tray is missing but something is preventing the tray from sliding in all the way, it lacks 1/4 " from being settled in brewing position.

SOURCE: Jura Capresso Problem

check out this link:
http://www.kuntze.de/E/index.htm

SOURCE: Jura Impressa E fails to dispense, then gives "open tap" message

I had the same problem, when I called their very helpful customer service, I was given these directions.
Take out the tray.
Inside the machine you can now see a flap hanging from the top.
Reach behind the flap, and you should feel a round object/filter. It has a little dimple sticking out in the middle.
Wipe the filter with a paper towel.
Put the machine back together, and voila you got your coffee brewing again.

SOURCE: Tray empty message

If the machine says TRAY MISSING it's the contacts at the back so clean as other people have stated, you can also use a cardboard nail file to clean the contacts at the back if there really skanky!.

If the machine keeps saying EMPTY GROUNDS even though you have, pull out the tray, look just inside the aparture where the tray goes top right at the front there is a small slot where if you look closely you can see a small white micro switch. This will be probably gunged up with coffee and the switch will be stuck up, get a can of WD40 and squirt a small amount up into the switch then poke the switch with a small screwdriver up and down until it moves smoothly.

Then replace all the bits, sit down, look smug and have a coffee cos you've fixed it!! :0)

SOURCE: How do I disassemble and clean the brew unit motor

I have some good instructions I downloaded from www.kaffeestudio.com . They are in German, but with many pics. If you are technically adept, then it is really no prblem. You should put in new o'rings and lubricate with the food grade silicon grease before reassembly, otherwise it won't be long before you are doing it again. Give yourself about 3 hours to perform this task the first time. One thing to remember. The cleaning tablets tend to strip the lubrication from the brew units, subsequently binding up the brew unit, sometimes tearing the o'rings and giving the malfunction 8. Plan on this being an ongoing maintenance exercise. Plan on at least once every year or two to have to do this.

SOURCE: Have reassembled the Brewing unit - am now getting Malfunction 8

oh dear that is too long without a coffee ;-( I was wondering if you could share your knowledge on how to dismantle the Jura coffee machine, i have a E85 and i need to remove old coffee sludge that is causing my problems. do i remove the back of machine?