Hi Nikola,
Thousand thanks for this plugin, this was exactly what I hoped to find... after trying many others! I have almost got it working, but in the final steps I'm a bit at a loss... and hate to say it... in a rush as well.
I have EA in the member section of my site. When I'm logged in as an admin everything works as expected.
But when I log in as a subscriber the calendar icon doesn´t stop spinning [[ea_bootstrap]] and I can't go forward with the reservation. When trying [[ea_standard]] the calendar works but the available time slots don't appear and the user name and email are not pre populated.
The member section of my site is created with WP-members plugin. If I unblock the page so that it's not behind the login, everything works again, but the user information is obviously again not pre populated (and I really would like this to be for the subscribers only). 
I have searched endlessly this forum and the forum in the wordpress.org, but haven't managed to find any clues of where to go from here. I really really hope you can give me some tips.
WP-members, Easy Appointments and Wordpress are the latest versions.
Many thanks in advance!
Petteri