In case you need it, here are PDFs of the latest Axis and Allies rules from the official manufacturer, including for Europe and Pacific 1940:
Upgrading industrial complexes
-
When an industrial complex is upgraded, can it be used the same turn? Thank you!
-
No.
Europe 1940 Second Edition Rulebook Page 22
(If you are upgrading a minor industrial complex to a major one, you may still only mobilize up to 3 combat units from that industrial complex this Turn.)A good rule of thumb is that you can only do/use something based on its status at the very beginning of your Turn. Such as landing planes in a newly captured territory, going though a canal or using a Naval Base. At the beginning of your Turn the industrial complex is a minor thus only 3 units can be built.