Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/02927d3b8b4bf478fd45b8a00b678dc2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563