Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4a3374d5e137e6989d573bbe27a71a38.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563