Edit a PO on a change order

we have a P.O. that was created from a change order.  We need to change the quantity and cost on it because the vendor can’t supply all of the product on time and we need to add a new item to the PO for and alternate product. PO is still open and nothing has been received or an AP bill has not been created.  Usually you can just put the PO on hold and make changes, but it is greyed out.  The Change order is also still on hold.

we are running 2020 R2 (20.212.0038)

Thanks

Andrew