I'm having the same issue - I've enabled to show beta downloads, but nothing comes up. It gets stuck loading the new list. Any ideas? Thanks!
Please check to make sure you have Object Desktop 4.01 installed. If not, download you can download it from https://cdn.stardock.us/downloads/public/software/objectdesktop/ObjectDesktop_setup_sd.exe
You will need to be logged in with an account that has an active Object Desktop subscription.
As noted above, make sure the Show betas downloads option is enabled.
And lastly, if you are still not Curtains, press F5 (while Object Desktop is the selected application) to refresh it's data.
Hope this helps.