The following are possible reasons why a kitten may not meow or has a hoarse voice:
Excessive shouting: This may be due to the kitten shouting too much, resulting in a hoarse throat.
Poor diet: If a kitten's diet is poor and it is not getting enough nutrition, it may also cause its voice to become hoarse.

Stress response: When kittens first arrive at their new home, they may experience a stress response due to not being used to the new environment, which can cause their voices to become hoarse.
Indigestion: If a kitten has indigestion, it may also affect its vocalization.
Health problems: If a kitten has throat or other health problems, it may also cause its voice to be hoarse.