Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/75246ae4c9c9e66a910d097b9edc11b8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563