That website allows you to check if the site is up or not. For me it is returning that the site is up, and I can access plcsimulator.net without any problems.
The simulator is working just fine.
Yes, triple digit users is a routine day there.
Your ip (212.x.x.x) is just fine so no need to spoof a different one.
My guess is either:
You're using an Apple product to access it
You disabled Flash
It's certainly a local problem so if all else fails I suggest trying a different computer