Being unable to be happy means being Miserable
Sad
"Illiterate" means unable to read or write.
greatful is another word for happy
Unable
undoubtedly
The prefix "un-" could be added to the word happy to create the word "unhappy," which means not happy.
HELLO!
Healthappy (healthy and happy)
Inimitable!
The word you are looking for is "mute."
Inexplicable
Cheerful is another word for happy.pick up a thesaurus and look for happy.