Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/da9cf7aa255469fa0b5dd76d3f944ab1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563