In the FAQ it suggests emailing info@openproject.com to request a Sandbox/admin access. https://www.openproject.org/projects/openproject/wiki/FAQ#6-How-can-I-get-administrator-rights

Unfortunately this email address is invalid and the message bounces back. I am assuming the correct email is info@openproject.org and have forwarded this on accordingly, but thought it might be worth flagging this here.

Thanks, I have changed it to info@openproject.org.