WHMCS Multisite Provisioning

I'm getting - Invalid data or no response: The receiving plugin may not be activated at: http://acupuncturetreats.com

The strange thing is I ran a test with this just yesterday, and it worked just fine. To try debugging it:
1. I verfied that the login settings in the WHMCS backend for acupuncturetreats.com are correct by logging in.
2. Checked acupuncturetreats.com Network Admin to check if the plugin worked but just didn't get the right response. (While testing yesterday it did correctly set up the blog but showed a failure. Trying again to approve the order said it was already set up.) The blog isn't set up.
3. Pinged acupuncturetreats.com from the server to verify there wasn't any DNS resolution wonkiness.
4. There is no 4. Don't know what else to try.

I don't mind debugging this myself - if you've got debug code or logging, I'd be happy to look myself, but I'd like a starting point. Need to know where to look to see what's happening. Thanks, Arnold.