DC17 Won't Suck Up

A common issue on the DC17 model is the suction disappearing, and eventually the motor turning off. The issue is likely a very easy fix. A lot of people have gotten rid of their Dyson altogether when they could have solved the problem in less than a minute.
The likely reason your DC17 has lost its suction is because the seal at the bottome of the cyclone assembly is not as tight as it needs to be, so over time, if the bottom of the bin is not closed precisely each time, it will push up on the rubber seal, and little by little over time, push it up.

When that happens, the seal is broken at the bottom and much of what is sucked up is sucked in through the cyclones and onto the filter instead of staying in the bin.

Naturally, that blocks the airflow which decreases the suction, which stops air from coming in the motor to cool it off, which causes it to overheat and turn off to cool down.
The solution is simple, just open up the bottom of the bin and pull the seal back into place all the way around (yes, you will have to wash your hands when you are done).

It should like the picture below when you are done. If you want, to keep it from being an issue any longer, you could put some super glue on the inside of the seal at the top where it locks in to the cyclone assembly.