I honestly have no clue how you got it to work with port 443 because Facebook chat doesn't use HTTPS and XMPP is port 5222 regardless. But I also had issues with connecting to Facebook Chat for most of the day, so the issue may have been on their end. I unfortunately had to delete my account details from the phone and re-entered them in. That did nothing, so I reset the phone, still no luck. Later on, I connected to a public Wifi signal, successfully connected and then switched back to T-Mobile's Data and all has been well since. If the issue continues, its most likely that the network your attempting to connect to has that port blocked.