Hi,
The reason could be that there is another condition record maintained for the condition type JMOP with the same material and that condition table lies above the condition table for Plant / Vendor / Material in the access sequence maintained for JMOP.
You may go to PO - Invoice tab - click on taxes - click on analysis button - Now, expand the condition type JMOP. Here you could find which condition record has been pulled and from which table. If not, please post the screenshot of "analysis" window.
Also, ensure that the condition record for JMOP with V0 tax code is not having deletion indicator.
Regards,
AKPT