Can't connect to Quick Support

I have a paid version of TV 13. I ask potential clients to download QS V13 off TV website.

I have had 2 instances in the past 2 weeks where TV13 says "connecting" and QS says "ready to connect", but connection never happens.

Ended up using deadsimplescreensharing but if they become clients, QS MUST WORK.

Any ideas on what might be wrong? I can use TV13 to connect to others running QS...