Hi JosephE
There are still a lot of bugs in Inventory in AR2022, and your issues is likely caused by one or more of those bugs. For example when deleting/editing/reversing an existing transaction, MYOB does not always update values correctly, causing a zero value. Autobuilds also don't always adjust values correctly.
Note that the approach suggested by Mike_James to force a re-edit of the invoice by adding a full stop will re-edit the invoice using 'current' values and settings, not those at the time of the original transaction. Your current value for this item seems to be zero, so MYOB will use zero, hence no change. If you do an inventory adjustment to set the value to the correct average cost, then re-edit, MYOB 'should' redo the invoices with the current average cost.
Regards
Gavin