EMPTY GROUNDS warning will not reset

The solution was referenced in one of the earlier postings but I wanted to clarify in case people are misunderstanding. The two metal contacts at the back of the machine insert into the wall of the machine and tell the coffee maker that the tray is inserted. Sometimes the big, flat, readily visible portion of these contacts get dirty and I think people are focusing on this portion of the contacts. However, the metal contacts also bend down into the tray where they can detect water (basically if there is enough water or material to conduct between the two contacts then the machine tells you to empty the try). This is the portion where you need to focus on cleaning, down in the tray, between the narrow plastic valley at the back of the tray. It will require Q-tips or something to really push down into the tray to clean away from the contacts. I did not have water in the tray but had enough moist old coffee grounds that it was causing the issue. I cleaned this area with water, a toothbrush and Q-tips and ensured it was very clean and dry. I have not seen the issue again in months (my coffee maker is three years old, gets used daily and we keep it relatively clean, but this is the first time we've gotten this error).

The tray metal contacts are just for water level in drip tray.
You need to ensure the rubber gate on the grounds tray is inserted correctly.
Also you need to look inside the machine where tray goes and ensure the waste outlet is clean as it can build up with grounds.

Just want to add another kudos for those who pointed out the importance of cleaning the area where the metal contacts bend down into the tray. I spent half an hour cleaning/buffing/drying/sanding the contact tips on the tray as well as the female receptacle inside the machine before stumbling onto that suggestion.

The area between the contacts on the tray, where they bend at a 90 degree on the back of the tray, was not even visibly dirty or scummy, but nonetheless I scrubbed it with a toothbrush, steel wool, and a lot of hot water and the problem was fixed.

S9 Owner for years, had every problem conceivable, returned many times for service. Contact cleaning, tray cleaning, area around and under tray cleaning inside all work, but the problem will always grow gradually worse. The empty grounds problem was finally resolved to be in the chute to the upper left where the used grounds come down and out. The access is difficult, you have to tilt on 45 deg and use a flashlight. With a tool or finger and napkin you have to get up in there and get the built-up grounds out! Those grounds collect over time, get caked and dried. You have got to go in and get it all cleared out. Or, return for service and they will do the cleaning for you. Good machine, a real firend, but it is complex and becomes grumpy.

I have been having this same problem for a while. it has progressively got worse and harder to clear. I had spoken with Cappresso numerous times and I was about to give up and send my machine in for repair.
Looking at the contacts on the tray, I noticed that they bend down into the tray along a very narrow trough. They were very dirty at that point. I used a old toothbrush with soap and scrubbed the contacts and the trough clean. My problem was eliminated.

We have the same problem. Several times we've taken a cotton swab to clean up inside the machine where the grounds come out. This helped a few times, but not all. The waiting may work, and we will try that out. Any ideas on how to prevent this (i.e. cleaning or servicing would really help.)

I called Capresso and they suggest running cold water over the two contact prongs at the back of the machine for 20 seconds, then replacing. This works about 75% of the time... but is irritating. I also cleaned the contacts but this didn't have any effect.

Ours did the same, I think it was a build up of damp grinds on the contacts in the back of the tray cavity