I found this old topic but it was locked:
old topic, but your comment about not going to fire after the plugin has already been activated is still valid. I have network activated Gravity Forms in a Multi-Site environment and after the activation I've added the define(‘GF_LICENSE_KEY’,'YOUR_KEY_GOES_HERE’); in the wp-config.php. This doesn't work indeed.
Solution: Deactivate, uninstall, reinstall and the plugin is activated in all sub-sites.
The problem I have is that I cannot simply delete gravity forms from my multisite install as I have a number of sub-domain sites already using it.
I added the serial# to my wp-config file, but now when I create a new sub-domain install, and activate gravity forms, the license and recaptcha keys don't show as filled in and activated.
Is there any way to get this working on sub-domain sites now that I have already got gravityforms running?
*Is it supposed to automatically fill in those fields on the customer sites if I have it in the wp-config file, or does it just stay blank and the customer has to trust that it works?