I came in to work today and discovered that all webmaps were stopped.
That URL is NOT supposed to be Forbidden?
Those are our maps.
Our ArcGIS Server is clustered and our INTERNAL maps are working fine... But all of the Externals are broken.
I checked your pages in the above link. They work. If the trouble seems to be on your end, check with your IT folks if there were any OS upgrades recently. You can also stop and restart IIS and do the same for each of your Map Services.
I'm not having any issues with your pages (or ours). Do the normal reboot, flush the browsers etc.
Any chance that your AGOL account has expired (i.e. annual maintenance not paid on time)?
If still having issues, I would contact support. http://support.esri.com/request-case
Seems to be working now.
If the internal maps work and external stopped, I would have started looking at your reverse proxy. Doesn't seem like AGS was the culprit.