The airways are blocked.
Switch the vacuum cleaner off using the On/Off footswitch.
Remove the electrical plug from the socket.
Disassemble the floorhead, hose, handle, and telescopic wand.
You can carefully push coarse particles which are jammed in the hose or in the telescopic wand toward the floorhead using a long object (e.g., a broom handle).
Items causing a blockage are usually easy to shake out of the handle.