Hi
Betfair should have emailed you if your account has been restricted in some way.
I suggest to monitor a few other markets e.g. soccer, horse racing just to determine if the same behaviour occurs. Traded volume should steadily increase. If those markets work ok, then it's probably a glitch.
You can also log in to your Betfair account on the website and place some low stakes trades, see how it goes, and watch the volume figures on the website, if they are delayed when you are logged in to the website then you have a restriction.
You mention demo mode, or test mode, if you use it a lot it's always good to place some real bets from time to time.