The current user has insufficient permissions to perform this operation when trying to add Term stored managed navigation.

Hi,

i am getting this error "The current user has insufficient permissions to perform this operation." when trying to add the Term store managed navigation like the following screen shot. i am the Farm administrator and as well managed services account. also noticed, cannot delete the service application, saying you don't have enough permission to delete the db. but using this account i was able to do everything before in my environment. is anyone already face this kind of error, so what will be the way to resolve this?

Appreciated!