First you'll need to get the AP reconnected to HiveManager (a red LED means the AP is not connected to a HiveManager). This guide reviews how to manually connect an AP to HiveManager (formerly NG): https://thehivecommunity.aerohive.com/s/article/CAPWAP-Guide-for-HiveManager-NG
Then you'll want to push a complete configuration update to the AP, which this guide covers: https://thehivecommunity.aerohive.com/s/article/How-to-push-a-configuration-update-to-a-device-in-HiveManager
If you're using HiveManager Classic, you'll want to use these guides instead:
Connecting the AP: https://thehivecommunity.aerohive.com/s/article/CAPWAP-HiveManager-Classic
Pushing a configuration update to the AP: https://thehivecommunity.aerohive.com/s/article/How-to-push-a-configuration-update-to-a-device-in-Classic
