You’re seeing the error message You already have the maximum allowed of that type of that equipment in the project, when trying to add irrigation equipment, but haven't added many models of that type of equipment.
You may also see a nozzle list showing duplicate sizes when placing a specific piece of equipment, such as a head.
An exact duplicate of the equipment with the duplicating nozzle sizes has already been added to the Irrigation Manager. (It will still only show as one listing in the Manager.)
1. Delete the duplicated equipment from the Irrigation Manager completely. You’ll need to delete it twice.
2. Add the equipment back to the Irrigation Manager.
You should now be able to add equipment of that type again.