This just started the other afternoon on Chrome, Safari, and Firefox (which are the ones I've tried). I'm using a Mac (v10.12.3). Chrome is up to date (v58.0.3029.110). Firefox does not give the error message; Chrome and Safari do give the error message; but the workshop does not work on any of them. 😕

What does the error message say?
What is the browser console reading?

The error message says, "Your browser or graphics card does not support WebGL." The console (in Chrome at least) is completely empty even when reloading the page or visiting it afresh—however, if I hit "escape," the message disappears, an extremely warped and unusable apparition of the workshop appears, and it says

workshop.obf.js:1 Uncaught TypeError: Cannot set property 'cancelKeys' of undefined
at UI.closeAlert (workshop.obf.js:1)
at _0x1cf237 (workshop.obf.js:1)
at dispatch (jquery.min.js:3)
at v.handle (jquery.min.js:3)

which may or may not be what you are looking for. 😕

So weird.

I think I know where the second part of the error come from - Don't worry about this one. Because webGL is not found as being active, it doesn't load everything and throw an error.

I am not sure why it says that WebGL is not active. Can you try this: http://www.doesmybrowsersupportwebgl.com/
Is this page working: https://stemkoski.github.io/Three.js/HelloWorld.html

Umm....okay, this particular situation is getting stranger and stranger.

1. I forgot to mention that the error message also gave links back to the home screen and to this page here, which says, "Hmm. While your browser seems to support WebGL, it is disabled or unavailable. If possible, please ensure that you are running the latest drivers for your video card."
2. Conversely, the "doesmybrowsersupport" link has in big bold letters "NAY."
3. And the HelloWorld link is acting very, very strangely. It seems to be fine, but the ground plane is only showing up half-way and after a short time it begins to act quite oddly indeed with warping and stretching and clipping issues.

Looks like you have an issue with webgl or your graphic card.
Before loading the workshop, I detect if your browser has webGL activated. If no I display the error message that redirects you to the get webgl page. If everything is ok, I load the complete script.

On this page https://get.webgl.org/ you shall see a cube spinning like described.
What kind of Mac do you have?

I have a MacBook Pro (13-inch, Mid 2012). The link has no cube spinning, nor anything describing it....I just tried the workshop on separate Mac of the same make and the same issue is happening, so perhaps it's an issue with this particular model?

It doesn't look like it is related to Mecabricks though. Nothing to report on my side. It is working at home on my Macs (Powerbook from 2009 and imac 2013). and even on my parents computer (2007 iMac).

I don't have 10.12 installed though.

You have options in Safari to enable or disable webgl. Did you check how they are set?

...and just as suddenly as it stopped working it began working again. WebGL was also broken on another Mac Pro (2014 model) so I have absolutely no idea what on earth was going on.

I guess the solution for this issue is "wait." 😕