I don't see any reference to a 'pin'. Looks like the Release Handle is held on by something like a keyway and secured with a set screw - common practice for that type of mounting. Above page from the Service Manual makes it look fairly simple to replace the Release Handle. Did you rotate the new Release Handle clockwise after you installed it on the top's linkage? Without doing that, I could see that the location for the set screw would be near impossible to get at.