In certain cases, the following error will appear when saving an item:
The following UOM codes are unavailable for use in the Unit Configurations: {unit(s) of measure}. Please add them as Input UOMs or reconfigure the involved unit configurations.
Go to Item Aspects > Unit Configurations. You should see one or more unit configurations using the unit(s) of measure that are shown in the error message. At least one of these will not be linked to the item either as a base or input unit of measure.
The easiest way to fix this is to add the unit(s) of measure to Units of Measure > Input Units of Measure.
Changing the base unit of measure is another option, provided that there are no existing transactions for the item.