"https://open-science-mooc-invite.herokuapp.com/" link to join github organization is showing internal error.

[kiranmuddam]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://open-science-mooc-invite.herokuapp.com/'
2. Enter github username.
3. Click on 'Add me to organization'
4. See error

Expected behavior
This page should process the username and send a join invite through email.

Desktop (please complete the following information):

• OS: Windows 10
• Browser : Brave Browser [ chromium 81.0 Build]