Generally Available: Windows Server 2012 and 2012 R2 Extended Security Updates enabled by Azure Arc

I’ve resolved the issues.

There was a problem with the CSP Tier 1 ESU order, which was addressed last week.  MS provision the skus, so the ESU updates could be ordered. So, if you need a MAK key (for Air Gap systems), place an order with a CSP Tier 1 and they will provision the key to your Office 365 tenant. The key is a subscription key for the period of October 2023 to October 2024. If you need a standard Server 2012R2, you need to purchase a 16-core license (minimum purchase for server 2012/R2)

This is what you need to do for Air Gap servers.