I got all stats for it but still cant ??

You sure you're looking at your mercs stats and not your own?

Also, your merc might be using a weapon that gives + stats and taking off that item might make him not have enough strength to wear bonehew.

nah, im way over stats required ..... i dont know why

Unequip his armor and helm and re-equip and try again.

if you use warlock and levitation mastery, item show stats req for you

right on , all this cuz of levitation...thx