AP downpayment Issue

Hello guys,

I came across an issue with a downpayment.

Under AP downpayment request an advance payment of Rs 500000+ GST 28% paid to vendor. For which, we have received a invoice with Tax @ 18%.

The vendor also refund the tax difference amount. Necessary entry made for both.

But still AP downpayment for tax difference is pending & its showing in Open list.