Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5c38e9e194dcc0f2aa7f6726d884a7a3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563