Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/4a7d25a7417ed69c39b2f60b8a2b9657.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563