User has db_owner through AD group but cannot create table
There are so many possibilities, but here are a few things to check:


that the user is a member of the ADB group in the Active Directory.
that ADB exists as a server principal (a login). Example: SELECT * FROM sys.server_principals WHERE [name] LIKE '%ADB';
that this login has a user in the database in question: SELECT * FROM myDatabaseName.sys.database_principals WHERE [sid] IN (SELECT [sid] FROM sys.server_principals WHERE [name] LIKE '%ADB');
that the database principal (the user) is a member of db_owner (not to be confused with schema ownership)
like @mlachman points out in another answer, that the database principal hasn't been specifically denied any actions.


Also,


You don't need db_public, db_datareader or db_datawriter on ADB, if it's db_owner. Good housekeeping to clean those memberships up, and it may even help with your problem.


If it's any use to you, I've written a script that compiles all of the permissions in a database. It's available on the Downloads page of my blog, and it's completely "as-is", without any warranty or guarantee.