Hi Guys,
Today I had to create a template for our remote session servers. Unfortunately, the System Center Virtual Machine Manager was greyed out.
Solution: VM has to be created in VMM.
After option became available I was able to run Create Template. But it failed, I tried manually without success.

Then I had two hours session with duckduckgo and google. I tried all the solutions. No success.
Then I decided to play with registy and read logs in C:\Windows\System32\Sysprep\Panther
I still didn’t have a clear solution however, I found out that Network Monitor was blocking. Uninstalling didn’t help. But I was sure that cleanup can’t success.
I went to “HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\SysPrepExternal\Cleanup and deleted one registry key which I had.

After that, I was able to run Sysprep and create a template.
I have hope that this helps you guys.
Have a good one!