If you can't login on my demo (for example with Safari), that's due to your browser settings. In the Preferences, search for something like "Website tracking" and uncheck "Prevent cross-site tracking".
You can use the following accounts :
John : email = john@demo.com / password = azertyuiop
Jane : email = jane@demo.com / password = azertyuiop (sponsor : John)
Chris : email = chris@demo.com / password = azertyuiop (sponsor : Jane)
Mickael : email = mickael@demo.com / password = azertyuiop (sponsor : Jane)
John : email = john@demo.com / password = azertyuiop
Jane : email = jane@demo.com / password = azertyuiop (sponsor : John)
Chris : email = chris@demo.com / password = azertyuiop (sponsor : Jane)
Mickael : email = mickael@demo.com / password = azertyuiop (sponsor : Jane)