Keep the axe on hold try this first.
Ok first thing to do is remove & clean the 2 piece premotor filter or purchase new.
Now remove soleplate from bottom of machine to do this rotate the 3 plastic screws to unlock position. Lift sole plate off now remove any blockagers or fluff that may be built up over the brush roller.
Remove hair from brush roll using scissors.
Check short clear hose for blockages & any damage rips or tares if it is damaged purchase new hose.
Now look at belts & rotate brush roller it should turn relatively easy if it is difficult to turn by hand remove the brush roller & pull off the end caps the axle will come out with one of the caps.
Check the roller bearings clean away dust build up replace end caps & axle spin roller holding on to end cap if freely to spin refit back on to machine.
If its stiff to rotate you will need new roller.
Now pull off the 2 inspection ports check them for bits of paper etc especialy the (U) shaped port at bottom rear of machine this can contain pens pencills stones all sorts of items that hinder the suction.
Now check the long flexi hose & metal wand for any obstructions.
If after all this machine is still not working correctly go to this site http://dysonmanuals.llc.nu/
On this site you will find Dyson service manuals covering poor suction, clutch,motor, etc.