This typically means you don’t have enough public watch hours, or that our review team didn’t reach a clear decision during the 1st review, so we’re putting extra effort/resources into additional reviews before making a final decision. More here: https://yt.be/help/YPP-review
AdSense accounts are typically suspended for invalid traffic or policy reasons, use this troubleshooting guide to help figure out what happened and next steps: https://yt.be/help/mdZm . If you still need help after that, reach out to Creator Support: https://yt.be/help/partners