I have installed a couple of 2016 standard recently. Both had the same issue. I believe this to be a bug. In both cases, the ""Settings"" button on the logon screen doesn't work, and the ""Theme"" tab doesn't have any information pertaining to changing the interface. I found two ways to change the interface: 1. Run the launch32.exe program, and 2. Delete the Sage 100 folder (as Kenny mentioned).
It doesn't seem probable that Sage would have intended the user to be able to toggle between 100 and 100c without paying for 100c. if they did, I don't believe they would have disabled the Settings button and the Theme information in Standard.