Hello 334jr,
Thank you for posting in Microsoft Community forum.
I'm sorry to hear that you're having trouble activating your Windows Server 2012 R2 Essentials. Since you have the product key and proof of purchase, you should be able to activate your server without any issues.
First, make sure that you are connected to the internet and that your server can communicate with the Microsoft activation servers. Then, try activating your server again by following these steps:
- Open the Server Manager and click on the "Local Server" option.
- Under the "Properties" section, you should see an option to "Activate Windows". Click on it.
- Follow the prompts to enter your product key and complete the activation process.
Also, I would like to remind you that since the 2012 version of R2 is no longer supported, this may also be the reason why you are experiencing the current issue.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Haijian Shan