Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2142e2b3a2d8eef85e84120c1164b597.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563