Purchase order & not created in company code &

What causes this issue?

You have entered a purchase order number that does not exist in the
company code in which you are working.

How to fix this error?

Check the PO number and the company code.
If the purchase order number is wrong:
Correct the PO number.
If the company code is wrong ...
... and the current screen is the initial screen:
Choose F3 and start processing from the beginning.
You can now enter the correct company code number
and re-enter the purchase order number.
... and the current screen is the <LS>New item</> processing screen:
Choose <LS>Cancel</>. Via the menu <LS>Edit</>, you can then
change the company code. Then you can re-enter the
PO number via <LS>New item</> --> <LS>Purchase order</>.

Error message extract from SAP system. Copyright SAP SE.