You’ve probably seen this message before and there are a range of potential causes for it.

In this case I battled with this one for longer than I would like to have before stumbling upon Ken Lasko’s “Meet URL Gives 404 error” and the fix. Thank you Ken!!

My meet URL (“https://meet.contoso.com/…”) was pointing to my Director and failing 100% of the time with joins from the client as well as the browser/silverlight “?sl=1” alternative:

Thankfully I could re-point DNS to the FE pool while I investigated this.

As in Ken’s case the issue turned out to be with the “IIS URL Rewrite Module 2”, however my initial attempt at just performing a Repair on that component failed because the version currently installed differs to the one that’s on the install media (which if you’re looking you’ll find in …\Setup\amd64\ as “rewrite_2.0_rtw_x64.msi”):

Here’s how I fixed it:

1) Uninstall the re-write module completely (from Control Panel):

2) Re-run the Bootstrapper, which reinstalls it – but as the original version from the SfB media:

3) Re-run the latest cumulative update to patch it back to the latest version:

… and from here you should be good. You might want/need to perform an IISReset to be on the safe side. I opted to bounce the box. I always prefer to cleanly boot a machine after performing any uninstall/reinstall operations.

And thanks again, oh mighty Hoff.

– G.