Getting access to LOOP
LOOP no longer uses an AD group. Signing in through Nexus One isn't enough on its own — you also need a LOOP grant in Nexus One's Credentials system.
How to get added
Contact an administrator to be added in Nexus One's Credentials area. There's nothing to request inside LOOP itself — your grant is checked automatically the next time you sign in.
If you were just added and still can't get in
Like the other apps in the suite, your entitlements are only re-checked on a fresh login. If you were already signed in before being added, sign out of Nexus One (which signs you out of every app at once) and sign back in.