the thing he grabs, is it the rail along the belt or the chain? And do you have the chain on the belt or is it still up on the platform?
To get this to work, first make sure you go down the belt (crawling along the rail) to the anchor to see Glottis, then come back up to the belt. If the belt is moving up, you should have no problem going up it, but if it is moving down try pressing and holding the shift key to run and try to keep Manny in the middle of the belt going up it. If you want off the belt, watch to see Manny looks at the switch on the belt and press U. This should make Manny automatically get off the belt.
As for the puzzle, make sure you took off the scoope with the Bust-All and you have the belt moving down. Then get in the crane and lower the chain. Switch the belt to move upwards to bunch-up the chain, then switch the belt downwards to loop it around the anchor. Then get back in the crane.