@hlzhang you can clear your cookies and cache and use chrome browser with incognito mode on and try again! If you get that Message again wait an hour and try
It's doubtful a new sim is invalid. Clear your cache and go into incognito mode and try again.
The numbers are very small so be extra careful youre entering it right.
Got a sim card from walmart. When I try to activate, it always said 'Invalid SIM'. Any one can help here?
Saadly, there has been the odd instance of a previously activated SIM being sold by Walmart. If the previous suggestions fail, I suggest you return to Walmart and ask for an exchange.
@hlzhang If you got the invalid sim message the first time you tried activating the card then it's possible that the card was previously activated. My recommendation would be to take it back.
The same thing happened to me. I returned to the Mobile Shop and Sim was removed and inserted again. The Koodo info had to be cleared and then everything was fine. It happens.