Hello There,
Thanks for contacting WPML Support. I will be happy to assist you in this matter.
I understood that the Migration code is not showing available on your site. I have checked our Subscription management system and found that both sites have an active Pay-as-you-go subscription. Kindly be informed that if both sites have an active subscription, connecting the sites and transferring credits between them will not be possible.
In order to solve it, kindly follow the instructions mentioned in the documentation below. I hope you'll be able to get the Migration code and share credits with other sites.