Needed to create users that subscribed to a list, those are being added only in the list but not in the WordPress user database, by checking the logs I found this:
[February 9, 2018 3:54 am] Request type “campaign” unknown, ignoring.
[February 9, 2018 3:53 am] Request type not defined
[February 9, 2018 3:46 am] Request type not defined
Site has SSL enabled using Simple SSL
Thanks in advance!