This could be for numerous reasons - it may be linked to the unique code for the organisation you are trying to add;
If the code has already been allocated to another level within your structure, the system will not allow for this to be added and you will see the below error message appear at the top of your screen;
You also need to ensure you are trying to add a level to one that you have access to. If you are trying to add a level to the Level '0' of WM Jobs, this may not be possible.
If you are trying to add a level to a level lower than this and are unable to, we would recommend that you check your user roles through User Management.