The Pro version activation actually takes place in the code free version’s code.
In the file happy-elementor-addons/vendor/appsero/src/License.php find the function check_license_status which starts on line 317 and add this to the start of the function code:
Then in the function is_valid which starts around line 337 add this to the start of the function code:
All done! Everything will be available. No need to add any license key or anything.