Check if issue is in test build: https://moot.it/startisback
But I guess it falls down to some setting or policy. Is Sleep available in modern ui shudown? Hi, I have the same issue (no sleep button) with build 2.1.2 on Server 2012.
I had a look at that link and I couldn't find the test build
You can enable the start screen in the "switching" configuration options.