EZLease on-prem v8.3 changed the way the account number groups database is structured. So, when you're installing v8.3, in order to make the needed updates, the user who is trying to open the Account number groups database needs to have "db_owner" permissions in SQL.
Before attempting the update (or reaching out for support), please update your permissions, or have your IT department update permissions, in SQL Server Management Studio (SSMS) to "db_owner"