Once your Rex profile has been created, you'll need to log into Rex through your Stockdale & Leggo intranet system.
The Stockdale & Leggo IT team have put this in place for you - so once your profile is created, the login from through the Rex website will no longer work for you.
If you're having issues logging in, you'll just need to touch base with the Stockdale & Leggo IT team directly to report this. One of their team will be able to help you further from there.