Thanks Aerin for your help.
Ok, I understand. But, in my evvent page I have the option to register anonymous users and also registered users
https://www.chiroeurope.com/events/chiroeurope-malaga-october-2015/
The problem is that, WordPress users that create, have only the first side of email address. So, for example, if I have
admin@bob.com and admin@juan.com it creates the user “admin”
I think that’s the problem. So, how you manage in your plugin to allow login?
Thanks a lot