If you're logged in but your firm isn't showing on the Join a Firm page, you've most likely signed in with the wrong login method.
Your account is tied to one login method — either Xero Single Sign-On or email and password. If you sign in using the wrong one, Cimplico Workpapers won't recognise you as a member of your firm.
How to fix it
Log out of Cimplico Workpapers.
Return to the login page.
Sign in using the correct method:
If your account is usually accessed via Xero, select Sign in with Xero.
If your account uses a username and password, enter your email and password.
Your firm should now appear under Your firms.