The inventory type field is not available to make a change to the type.

A:
Once an inventory item has transactions posted the option to change the type on the Item Master Maintenance screen for Settings is not available. This could also happen changing from non-stock to stock.

Try using Key Changes in System Manager. This will change all references in all transactions from the old item name to a new item name. The new item can now be marked as inactive to prevent the item from being used. For more information on key changes refer to the System Manager Doc on Disk manual.

Create a new item with the same name that was used before the key change and set the item type as active.