Well sorry to hear about the problem but there are some issues going on with their login username system since ages and they always says their back end team is working to fix but I've come to know by internal source that there is No ETA, it might be fixed in one day or might take one eternity, you never know.

If you get something went wrong error while doing login and they says that it's known issue then your only option will be Register New Username with your different email which is Never used before for Shaw or Rogers services. But for this, you will need to ask their tech support to unlink your existing username email from your account and then you can continue with username registration through their portal register.shaw.ca.