I'm sorry to hear that you NAT type is now showing as strict whilst it was previously open, I know how frustrating it can be when your gaming experience is affected. Let me see if I can help.
Firstly, could you try a wired connection in modem mode to see if the NAT type remains strict? It's also worth looking at port forwarding and considering putting the hub into DMZ if none of that works. I've run some checks on the hub just to make sure there isn't an issue elsewhere, everything looks good.
Just let me know how you get on, and we'll do what we can to help if problems persist.