Last few months my wifi has played up, constant buffering and can no longer watch tv online. After following online help, which is a nightmare when you're having trouble with wifi to begin with... apparently my signal into the house was good so it must be a problem with my equipment...paid £60 for a new smart hub as online troubleshooter diagnosed that was the problem, no change. Have moved hub more central in my house, no change. Have paid £8 for new filter, no change. I live right near junction box...what's the guessing I've paid £70 for no reason and the fault is not with my set up that hasn't changed in years?! Really annoyed!!!
You should ask for a refund for all you have spent and revert back to the hub you used before.
I did exactly same as you. Changed from HH5 to SmartHub/HH6 thinking it would be better. Was a total disaster. Tried all sorts of fuddling about with it - nothing worked. Changed back to HH5 and bliss - still get occassional drop outs while streaming but at least all devices connect.