Global CPA is not available to reference in Standard Purchase Order

I am not sure what i am missing, but I have created a CPA for supplier S and site as X in US OU. Check the global box and enable all sites.

From tools menu, I have added additional OU i.e UK for another site Y for the same supplier S. Save the record and approved the CPA.

Now i moved to UK OU and try to create the Standard PO. Try to pull the CPA to reference, but LOV is blank. What i am missing here?

Please help.

Thanks in advance.