If you're facing trouble logging in and accessing the materials, here are some troubleshooting steps:

Unable to sign in and got the message "Signups not allowed for this instance" / "Signups not allowed for otp"

Upon purchase, an invitation email would have been sent to the email address you used to check out. You have to click on the invitation link within that email to activate your account. You will then be able to sign in from the login page for future sessions.

Didn't receive the invitation/login email

  1. Check your spam inbox, it might have ended up there.
  2. Ensure you do not have custom filter rules that affect which inbox the email lands in.

Clicking on the login link doesn't sign you in

Some common reasons include:

  1. The login link expires after it has been accessed once. Your mailbox's spam filters might be visiting the links while filtering for spam and thus invalidating them. This has been a common issue if you use school emails (known examples include We can help you to change to another email address (Gmail recommended), just send an email to
  2. The site uses cookies for authentication. Make sure your browser extensions are not blocking access to cookies. To test if this is the cause, send yourself another link and open the link in incognito mode or another browser.
  3. Turn off VPN if it's running or use a VPN if you're not. Your local ISP might be blocking certain websites we rely on.

If you are still facing issues, reach out to us at