The red CON indicates that the vendor is not mapped to the equivalent Nexsyis vendor. Since Nexsyis does not know the vendor, it cannot create the Purchase Order.
You will need to manually create the PO in order to Receive, etc.
To resolve:
Double-click on CON to launch the Third Party Purchase Management screen

Next, on the left list, select the order line

Then on the right list, select the Nexsyis Vendor

Finally click the "Create PO" button at the bottom.

You will now be able to receive the parts as normal.
At the bottom of the screen, click the Vendor Mapping button

On the Mapping Assistant screen, select "Vendors" and "Unmapped".

Here you will see any unmapped OPS vendors.

Search for the Nexsyis vendor on the right

Then click the "Map" button.

Now future orders to this vendor will work correctly.