Error 503 Service Unavailable when trying to login to KnowledgeSync v10 Portal

Client reports the following:

"I have been in the middle of writing a report and was kicked out 4 times by saying the portal has timed out. 
Now I get this error when I try to log in. "
Error is:
"KnowledgeSync Alert
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN““http://www.w3.org/TR/html4/strict.dtd">
<HTML><HEAD> <TITLE>Service Unavailable</TITLE>
<META HTTP-EQUIV=“Content-Type" Content="text/html; charset=us-ascii“x/HEAD> < BODY> <h2> Sen/ice Unavailable</h2>
<hr> <p>HTTP Error 503. The service is unavailable.</p>
</BODYx/HTML>"

So far, here is what we've tried:

1. Stop and start the KnowledgeSync Service.
2. Reset IIS.
3. Stop the service and run KnowledgeSync as a Desktop Service.
4. Reviewed the DefaultService.log.
5. Checked to make sure Inactivity Time is set to the default - 20 minutes.
Opened up a ticket with KS Support this morning. Haven't heard anything back yet. Anyone have any other thoughts?