I also have the same issue. Running Windows 10 Enterprise 1809 (17763.55). I installed (and re-installed) Windows Admin Center 1809 (1.1.26146.0), but I cannot view the localhost site. In Chrome 70.0.3538.67 or Edge 44.17763.1.0, I get the page cannot be displayed if visiting https://localhost:6516.
I've rebooted and re-installed with no luck. I also tried the registry fix mentioned by Roberth. Nothing has worked. This was the first I found anyone else having this problem. I'm really hoping someone has a fix. Thanks.