Thanks for reaching out. Community posts are available to channels with over 1k subscribers. Note: it will take up to 1 week to see the Community tab after passing 1k subs. Here's more: https://goo.gl/NyDzE7 . Hope this helps explain things.
It takes 1 week to see the Community tab after passing 1K subs. Also, have you received any strikes on your channel recently? If you haven't, try enabling the custom channel layout for the Community tab to be visible: https://goo.gl/3gRYbR . Hope this helps.