one of the problems is that the bad guys use VPNs too and they do bad things and get one or more of the VPN's IP's banned.
99 times out of 100 when this happens here or other forums, just switching VPN servers fixes it.
ETA:
Its funny, a day or so after posting this, I found myself blocked from here.
Looks like both the Dallas and Washington DC IP addresses for ExpressVPN are blocked now. Great. :p