Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a8585b5aa70ec90949fc9f9c729259d4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563