ok Dimitris, I get this:
Server error status: Internal Server Error 
WE NEED YOUR HELP, BOSS!
Hang on a minute... It looks like your WordPress site isn't configured to allow one-click installations of plugins and themes. But don't worry! You can still install this plugin by entering your server's FTP credentials here:
CANCEL OKAY, CONTINUE!
We will remember these details for 15 minutes in case you want to install or, update something else.
Or you can enable one-click installations on this site by adding the following details to wp-config.php:
define( 'FTP_USER', 'your FTP username' );
define( 'FTP_PASS', 'your FTP password' );
define( 'FTP_HOST', 'soedev.com' );
It gives me the opportunity to fill in my password, but when I do it comes with the 500 error.
what to do? Piet.