I've had exactly the same problem this morning. That error was showing up when I was trying to install Void Bastards, but further down the page it said that I didn't have the correct version of windows. I think that's the real reason, not administrator privileges. The Administrator Approval error is probably erroneous.
The standard Windows Update page in the system settings is telling me that Windows is up-to-date, but it isn't. I haven't got the May update yet. After spending about an hour jumping through hoops trying (and failing) to get Windows to update itself, I've discovered that they have a "Windows Update Assistant" program buried away on their site that isn't linked to from any of the troubleshooting pages I was visiting. Really smart move there, Microsoft. It's here: https://support.microsoft.com/en-gb/help/3159635/windows-10-update-assistant.
I'm currently downloading the latest update via that, fingers crossed that will sort out all my problems. Hopefully your issue is something similar and this will help you, too.
EDIT: Windows is updated, and it has downloaded and runs just fine. It's also a really awesome game.
As someone who doesn't usually stick with one game for very long, I like seeing my playtime number hit milestones for the games I do play a lot of. It's nice to see that I've actually put a lot of hours into a game for a change.
2018 is a pretty bad time to be releasing an indie game on Steam in general. There is so much stuff coming out, great games get crowded out whenever they are released. These days to have a successful Steam game you either need to get very very lucky, or have fantastic marketing outside of Steam. Simply sticking it up on the Steam store isn't guaranteed to get your game noticed anymore, whether you do that during a Steam sale or not.
In fact, launching during the sale might lead to more exposure - not a lot of indie games are being released on PC because they're trying to avoid clashing with the sale, therefore it is probably getting more coverage in the media because there isn't much else for it to clash with. For example, if there were a ton of other games coming out right now, might it have been overlooked on Giant Bomb and not been given a Quick Look? Possibly.
@a2000: Those are both "Concept" pages, not game pages.
@twitchnmnr: Stream Avatars is not a game and the page has been deleted.
Can someone explain exactly what Marbles on Stream is and how you play it? If it is an actual interactive game that you play, it may be entitled to a page. I thought it was just a visualisation where you watch marbles fall, but if there is actual gameplay, it may be different. If the entire interactivity is you naming a marble then it randomly falls, then I'd say that's still just a visualisation, not a game.