ownership change

i am the owner, wanting to change to another person.

this person has ownership writes (he has a license)

i went to Share, select the person and then selected "make owner".

got an pop up the said he will get email that he has to select accepet or decline being the owner.

then i get another pop up that says the user cannot accept ownership...

i created a new sheet to test it out and i changed him to the owner.

do you have any idea why.