Beta 6 – can’t change skin on some installs

I have multiple 17 Beta 6 instances installed on various windows machines and android tablets. I was able to change the skin to Confluence on most except two windows machines (win 7 and 10) even though i had no problems on a 3rd windows machine (win 10)

On the two that can’t change, clicking on the default skin name doesn’t bring up the dialogue to change skin at all.

Any hints on what to do? I really prefer the Confluence skin because I can’t get thumbnail view on the default skin.

Thanks