Session error 40014 (SOLVED)
The disconnection error typically means that your connection isn't being routed to the game servers. Every occurrence of this that I've seen happen so far has been something like firewall rules, security programs causing conflicts, problems with old user data, etc.
If the steps other people have been able to use to fix this aren't working for you, I'd suggest using selective startup (you can find a walk through on this on the Microsoft support site) to turn off all non essential services and then try connecting. If that works, then there's likely a resource conflict occurring somewhere (which can be figured out by turning services back on in groups to narrow down which once caused the problem).
I suppose there also might be a chance that it could be caused by ICS or BFE needing to be reset.
Source - Quote #7594684