Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d27cf6c3dca89234a4d806e5adf9b0b0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563