Hey, what popup window? Do you mean the one with the license (EULA)? If that's the case, scroll to the bottom of it and accept the terms. The app should function normally then.
The code Execution cannot proceed because UnityPlayer.dll was not found. Reinstalling the program may fix this issue. - Thats the issue.
Try redownloading the app. You're missing at least one file (you might have deleted it). It should work if you just get a fresh build.
