Why does my Dyson DC37 lose suction after just 2 seconds?

When I turn on my Dyson DC37, it works for about two seconds with good suction. Then, I hear a sound as if something is blocking it, and it completely loses suction.

Here’s what I’ve tried so far:

• Disassembled and checked all parts of the hose and air pathways for any blockage—everything looks clear.
• Bought a brand new filter and thoroughly cleaned the entire filter housing.

Despite these efforts, the problem persists with no improvement.

Has anyone experienced this issue or have any ideas on what might be causing it? Thanks for any advice!
Cheers Pete