Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/20c3713ee0fb58d3b2c02067a7af84ad.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563