I cannot use "Open excercise system" link on System Architect Essentials I (7.1) and System Architect Essentials II (7.1) pages.

These are pages of "My Self-Study" page of Pega Academy.

I can actually go into the page of "Open excercise system" page if I click the  "Open excercise system" link of each training page.

But I cannot login from the "Open excercise system" page whre only login menu ( User Name, Password and "Log in Button") appears.

If I entered User Name and Password of my PDN account and hit the "Log in" button, the next page appears with the message "The information you entered was not recognized."

So I cannot use "Open excercise system".

Do you have any suggestions?

Thank you.