Deployment Solution - Preboot Configuration for WinPE Issue (ADK import issue)

While configuring the PreBoot Configuration for WinPE 10.0, I have installed the ADK and while trying to import, it gives me the message that DS is importing the ADK but nothing happens even after many hours. When I try to select WinPE 10.0 again it will again give me the option to import the ADK. 

I am using Windows Server 2012 R2 and running SMP 8.5 RU2. 
Also please help with the correct version of the ADK to be installed. As per the link - https://support.symantec.com/us/en/article.info356..., there is no mention of teh ADK version to be used for 8.5 RU2. 

Thank You in advance.