Thanks Vahidd for the help.
I did all the things I read in this forum, Check for spaces in the function.php file for example, and what did work was to replace the wp-admin and wp-content/plugins folders via FTP.
But still trying to understand if every time I install a plugin I could have this error?
What happen now with all the plugins I installed? need to be re-installed? BUH! sad.
Any chance to prevent this kind of issues?
Thanks,
Lorena