I work in information security, so I employ numerous tools on my personal network to guarantee safety when browsing on the internet.  For example, I use a VPN service, so that my device/location cannot be identified by websites.

implied in the site name -- skip the games -- and just never go so don't have to worry about such things.

I don't do STG.  I do run NordVPN.  It allows to select the country you want the VPN to be in.  Could it be country specific (IP's blocking certain countries?)

I use TOR (free VPN and a secure browser combo). Sometimes STG gets through, sometimes it doesn't. Same thing with Tryst: sometimes Tryst gets through, sometimes not. And so on for several other sites (even Google ["Too many inquiries from your IP address. We think you're a bot." errors. And Youtube is sometimes blocked. I rarely click on Youtube links because it's a waste of time -- sorry, Robertini, I rarely click on your many Youtube links.]  
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I hope I understand this correctly. TOR uses onion routing. Me--ConnectionServer1--Conn2--C3--C4--destination (e.g., STG). Every few minutes, TOR changes the Connection Links: Me-C12-C32-C3-C17-destination (e.g., STG).
STG only sees the last Connection Server. If STG doesn't like C4 or C17 for some reason, it blocks sending the info back through the chain STG--C4--C3--C2--C1--Me or sends an error message. Sometimes, the random connecting server is fine with STG's server and I DO get the page content.  
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Sometimes, it is TOR and the TOR Browser that detect unsafe code and block the webpage from getting through.
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Like the OP, I am not going to change TOR Browser or other settings to weaken my security just to see an ad or a Youtube.  
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I have repeatedly recommended to Providers with their own websites that they ask their webmasters to test the site (try to access the site) using TOR (more than once). If there is offending code that TOR or other VPNs don't like, modify the code!

It's not really exclusive to stg, many sites do this to a different degree.  

You are fine. Wix doesn't block many, if any, vpn ips as far as I know.  

Mya - I don't have any issues with your site.  Nor with any of your ads referenced in your profile.

Looking good using TOR!  
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I'm not a computer expert but I guess I shouldn't have specified "code" as much as settings or links.  E.g. #1, if the web site works with VPNs (as Wix seems to do), the Provider might have embedded a link to images or other stuff on a DIFFERENT web site that does block VPNs. So the basic page shows up but embedded material does not. That might have to be fixed by storing material (photos, etc.) on a different website that doesn't block VPNs and then changing the embedded links.
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E.g. #2, the basic web template might have some settings or switches that need to be checked on or off: "Check this box [ ] to block VPNs on the list of bad VPNs." or "... to ALLOW VPNs ...". If you or the webmaster forget to set the settings, it could block TOR and other VPNs.
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A related example is that some web hosting sites used to have a DEFAULT setting that required viewers to pay a fee to view the galleries. If anybody paid, the money went to the web site, not to the Provider. However, all the Provider had to do was change the default setting ("make 'em pay!") on her account to "Allow free access to my gallery." After web site upgrades or other maintenance, the setting might revert to the default "make 'em pay!" so the Provider just had to be alerted (by angry TER posts!) to log in and change her settings back to "Free gallery viewing!"