A few things to try...
1. Remove the blocked hose, switch the hoover on and poke the wrong end of the hose into the hoover, which effectively means the hoover sucks anything out of the hose the way it went in. This usually works.
2. Find a metal bar or a broom handle and drop it down the hose from the connection end to try and knock whatever it is out the other end. Make sure whatever you use slides easily through the hose and has no sharp edges or ends.
3. This one is a bit messy. Take the hoover hose outside, put your garden hose into it at the end that connects to the machine, and switch the garden hose on. This usually worked when I had to clear hoses on garage forecourt vacuums. The blockage often just floats out in the water. Give the hose time to dry before connecting it back up to the hoover though, so you don't get water getting into your Henry!
Mark L., May 2005