Despite the claims that the Dyson vacuum does not lose suctions, I've had occasions where mine has lost suction even after I've emptied the canister. What I found is that for the piece inside the canister that gets emptied, there are hundreds of tiny holes. If you vacuum up lint of the right (or wrong) size, it can lead to these holes getting clogged.

There is an easy fix though. Just get a short metal brush and have at these holes. It knocks out the lint that gets stuck in them, and you'll get full suction on your Dyson vacuum again.