I've had this issue through most of the 10.13 betas, it's quite strange. If I start the "App Store" app it starts normally, the the "Featured" screen showing. However if I select any of the other icons at the top of the screen ("Top Charts", "Categories", "Purchases" & "Updates") nothing happens, it just stays on the "Featured" screen. The only way I can install updates is to start Terminal and enter "softwareupdate -ia --verbose", and that works normally. I haven't seen anyone else having this problem, so I assume its not a common issue. Any ideas would be gratefully received.