Hobie support article on raising mainsail:
https://www.hobie.com/articles/sail-hoisting-and-halyard-locks,89/The part about batten tension is very important. Boat must be turned into the wind. Check for pinching/galling of the luff track on the new-to- you mast. If you have an old wire halyard with the second nicopress fitting for reefing, make sure it's not getting hung up in masthead.
Short of removing the masthead sheave, I expect you have to cut off one of the thimbles on the old wire halyard to remove it. The Hobie replacement apparently requires that the new thimble be pressed on after installation:
https://westcoastsailing.net/hobie-16-main-halyard-non-comptip/The Murray's replacement does not:
https://www.murrays.com/product/02-0273-50/