I have a similar problem. Usually in the morning (US EDT) the system seems to update several times (15 minute cycles) but then stops and I become TODAY not LIVE. I have noticed that if I stop Plane Plotter, close the program and then start again that FlightAware updates for one or two cycles then goes back to TODAY again. I check my PP uploads and they are normal. Based on the location of the site, I have coverage for 300 miles in at least have of the compass points so I should be adding data fairly quickly.
I tried using the direct connection to FA from SBS-3 but their was no difference.
I am now back to feeding (or trying) through PP as secondary server feed.