Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8f39fd8d55777af22ec43ba0e4a854eb.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563