Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d2c2f0641780f08ff1441240bea4dfdc.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563