Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5b5e65b525a3b4f74fa54f16be1b7872.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563