Hello,
This scares me:
I have so far noticed when I changed the code from a php file in my pro version folder under wp/plugin, it doesn’t change anything.
But when I change the same but free php file, the change shows.
What are you editing?
Activate & configure WC Vendors free. Then activate and configure WC Vendors Pro. Your accidental Pro first activation shouldn’t matter if you have now activated free- just make sure you configure free first now. Then activate Pro.