One reason might be that your plant is getting too much or too little water. Morning glories need well draining soil—neither too sandy, in which case water would run through it, nor too thick/composted which would cause water to puddle and not drain. (If you are using a container, does it have adequate holes?) Morning glories are tropical plants, so they need a lot of direct sun. Is yours getting about 8 hours of sun?
One reason might be that your plant is getting too much or too little water. Morning glories need well draining soil—neither too sandy, in which case water would run through it, nor too thick/composted which would cause water to puddle and not drain. (If you are using a container, does it have adequate holes?) Morning glories are tropical plants, so they need a lot of direct sun. Is yours getting about 8 hours of sun?