I've been unable to get the SimpleRESTSOE to work. I'm getting the error message, Invalid URL when I hit the SOE using http://<server>/ArcGIS/rest/services/<service>/MapServer/exts/SimpleRestSOE I am able to get SimpleSOAPSOE to work.
Yes, I see my extension on the bottom of the list of extensions.
I've also programmed another extension, and it doesnt work either. And all the proper stuff seems to show up in the config files. Thats why I setup the out of box SimpleRESTSOE - so I can prove it wasn't my code.
I'm guessing it's something about security, but I'm not sure what? The crossdomain.xml and clientacesspolicy.xml look almost exactly like the ones on arconline, except our clientacesspolicy.xml added <domain uri="https://*" />