I can duplicate the behaviour in Manager v23.10.20.1089 Server Edition on Ubuntu 20.04 TLS. I created a new test-business and customized it with the essential accounts including Inventory. Then I issued a Purchase Invoice.
The Summary Screen shows a deduction from the Bank account, Accounts Payable and under Expenses Inventory-cost but it does not show anything under “Inventory on hand”.
After payment of the Purchase invoice the Accounts Payable cleared as expected but still nothing under “Inventory on hand”. I am aware that @Lubos has been working on Inventory and related and may have introduced this problem.
Exactly the same happens when bypassing an invoice and immediately make a payment.