You sign in from your organisation's address

This is the general LeavePilot address, not an organisation's workspace. Every company has its own, and credentials only work there.

The address takes one of these two forms

company.leavepilot.app

or an address chosen by your company, such as leave.yourcompany.com

Can't remember the address? It is in your invitation email, or ask whoever administers LeavePilot in your organisation.