If it a 'spring' only blind, not a pull cord, pull the blind down to its full extend and then let it wind back up as far as it will wind.
In that position, remove the blind from the brackets and roll the remainder up by hand.
Replace the blind in its brackets and pull the blind down to its normal extend.
The blind will now be tensioned correctly which will enable the blind to fully roll up
BlindGuy
February 2010