Also make sure that you are using 'Item Inquiry with Sales/Costs' as this one has the Transaction History lookup. The other 'Item Inquiry' that doesn't include sales and costs has fewer inquiry tabs available, and one of those tabs is the History.

As noted above, Security access to the Transaction History function also controls visibility to this tab, so if you are using Item Inquiry with sales/costs and don't see History, a likely culprit is security. Can you access Transaction History from the Inquiries menu, directly rather than through an item?