Can you guys surf the "practice" site? 'cause I couldn't open it.
Hmk... I wish I could pm you my email, but I think I understand what you meant.
Did you try refreshing the page? If that doesn't work, try using a different browser -- it could be the browser itself. What do you normally use -- PC or mobile?
I tried going to practice page with Duo, just fine. It's odd to see you cannot go on.
I hope it helps. Let me know how it goes if you tried all of the above. =) GL and I hope it works out!
Uhh, I used to use the Chrome to surf Duo, I change IE to follow your advice, but it still remain the same. Duo on mobile is ok to use, the PC gets more grammar knowledge to learn, but the practice on PC still couldn't show up after all your suggestions, anyway, thanks. I think I should use Duo's app to learn language.