Put an M960 crankset on my Trance yesterday. The Deore on on there was just HT not HT2. The front mech shifted fine across all the rings before. Now I've lost the granny ring. Undone the screws to allow it to drop that far and tried adjusting it. It won't go across all three rings though. It'll do the granny and middle or the middle and outer. Its a 2010 deore front mech. The spacers for Bb are 2 on drive side and one on non-drive (as it was on my scale). What am I doing wrong?

that sounds like a cable problem – if you can reach the extremes of the chainset, which you can even if only two at a time.

Measure the width of your BB shell, if it's 73mm then you have too many spacers, one on the drive side is all thats needed.Also check the height of the mech cage, should sit about 2mm above outer ring, you may have different sized rings to previously.

Undo the gear cable and start again.