Dear Luis,
Based on the debugging message, it seems you are missing "tx.php" which the script is looking in this path: /var/www/vhost/meeting-in.pt/httpdocs/staging/wp-content/themes/sentinel/ffOptions/sitepreferences/structures
Types plugin does not look for this script. Maybe its your theme. Can you please provide another debugging results message? Please enable the WordPress debug using these below lines to your existing wp-config.php:
// Enable WP_DEBUG mode
define('WP_DEBUG', true);
// Enable Debug logging to the /wp-content/debug.log file
define('WP_DEBUG_LOG', true);
// Disable display of errors and warnings
define('WP_DEBUG_DISPLAY', false);
@ini_set('display_errors',0);
Make sure there is no other debug.log that exists in the wp-content. Then replicate the fatal error again. You can then find the debug.log generated in yoru wp-content directory. Please post the results of debug.log here if its not too long. Otherwise if its too long, let me know so can send it to my email.
Did this error also occur when you activate Types plugin with other themes? If the fatal error only occurs with your theme, it could be a theme-incompatibility issue. Please let me know how it goes. Thanks 
Cheers,
Emerson