So you have decided to increase security by adding a banned password list but the option in Azure Active Directory admin center is greyed out. Problem is licensing. This feature is only available in Azure AD P1 Licenses as part of the Enterprise Mobility and Security E3.
The problem greyed out Password Protect
The issue, licenses, and no Enterprise Mobility and Security E3.
Upgrade to Enterprise Mobility and Security E3 License (please confirm further before purchasing)
Example Password List to Ban
Password_123, Manch35t3r, 123456, password, 123456789, 12345, 12345678, qwerty, 1234567, 111111, 1234567890, 123123, abc123, 1234, password1, iloveyou, 1q2w3e4r, 000000, qwerty123, zaq12wsx, dragon, sunshine, princess, letmein, 654321, monkey, 27653, 1qaz2wsx, 123321, qwertyuiop, superman, asdfghjkl