even I have a similar use case.
The user can subscribe and unsubscribe from our portal.
I used listBatchSubscribe() method to subscribe the user and listBatchUnsubscribe() to unsubscribe based on user setting in our portal.
When I again tried to subscribe user (via listBatchSubscribe method again) it giving the below error message
{"add_count":0,"update_count":0,"error_count":2,"errors":[{"code":212,"message":"xxx...@xxxxxx.com has unsubscribed, and cannot be resubscribed by you. To prevent false spam complaints, they'll need to resubscribe of their own free will.","email":"xxx...@xxxxxx.com"},{"code":212,"message":"xxxx...@xxxxxx.com has unsubscribed, and cannot be resubscribed by you. To prevent false spam complaints, they'll need to resubscribe of their own free will.","email":"xxxx...@xxxxxx.com"}]}
Please let me know how to subscribe again from API
Thanks