If you still haven’t heard back, it’s usually for 1 of 2 reasons – you don’t have enough public watch hours, or your channel requires additional, in-depth reviews since the content is close to not meeting our policies. More on these 2 topics here: https://yt.be/help/YPP-review
If you haven't heard back yet, this usually means your channel is being held for additional reviews (bc your content is close to not meeting policies). Take another look at Monetization policies & you can use this time to make updates. More here: https://yt.be/help/YPP-review