When a specific setting has been enabled in the Administrator to Allow Multiple Projects then it will only be possible to Add new Customers to a Project when:
The Project has never had any draft WIP containing any transaction lines associated with it.
This is including open (pending) draft WIP and processed (complete) WIP
**However a Project which once had a draft WIP that has only had allocation lines written off in it, can still have customers added to it**
**It is also possible to remove a customer from a Project. Providing:
There are no current open draft WIP
**Customers can still be removed from Projects, when the draft WIP have previously been processed**
To work out if your Project has had WIP entered against it, and so may be the cause of your Add or Delete button being greyed out (disabled):
On the Project Management Window, click WIP
On the WIP selection screen click History
This should show whether there are any draft, processed WIP on the project