User Sync not working, log not very helpful

Hi,

I am trying to sync two websites. In the dashboard, I don't get any error but the users won't sync. I activated the debug mode and I get the following logs:

Master

[2015-11-28 08:46:38][M] 0-10 - ajax actions***
[2015-11-28 08:46:38][M] 07 - added new sub site***
[2015-11-28 08:46:38][M] 0-10 - ajax actions***
[2015-11-28 08:46:38][M] 08 - count of users= 1;;***
[2015-11-28 08:46:38][M] 02 - sending request - url=http://a23.393.myftpupload.com/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-11-28 08:46:40][M] 03 - sending request - response=1fae7c1162d2c8565558f00f45f1e4b7;;***
[2015-11-28 08:46:40][M] 05 - checking key true;;***
[2015-11-28 08:46:40][M] 09 - user sync***
[2015-11-28 08:46:40][M] 02 - sending request - url=http://a23.393.myftpupload.com/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-11-28 08:46:50][M] 04 - sending request: something went wrong***

Slave:

[2015-11-28 08:46:38][S] 01 - new subsite conection - central_url=http://portal.thetheatretimes.com;; replace_user=0;; overwrite_user=1;;***
[2015-11-28 08:46:38][S] 02 - sending request - url=http://portal.thetheatretimes.com/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-11-28 08:46:38][S] 03 - sending request - response=ok;;***
[2015-11-28 08:46:38][S] 01_2 - sync users for new subsite***
[2015-11-28 08:46:38][S] 02 - sending request - url=http://portal.thetheatretimes.com/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-11-28 08:46:40][S] 0-10 - ajax actions***
[2015-11-28 08:46:48][S] 04 - sending request: something went wrong***

Both websites are on GoDaddy.