Hi Cliff,
It depends on the Barlow your using, they do vary a bit.
My Takahashi 2x 2 element Barlow requires inward focuser travel and my parks gold 2x 3element Barlow is pretty much parfocal with the eyepiece.
If you have run out of focuser travel try sliding out the Barlow or eyepiece a little with 1 or 2 extensions to see if it reaches focus.
Good luck
