Why can’t I change the unit template for a specific material?

There are two possible reasons for this:

• Lacking the required permission: managing units requires the “Edit General Settings” permission. If you don’t have this permission, the “Manage Units” button itself appears completely disabled, with a tooltip shown on hover: “Requires Permission.”
• Existing transactions recorded on the material: even if you have the necessary permission, if the material is already linked to a unit template that has transactions recorded in the system, the “Template” selection dropdown within the “Manage Units” panel appears disabled, and the option to create a new template is also disabled. In this case, you can only add new factors (units) to the current template, without replacing it entirely, in order to preserve the integrity of historical data.