Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2697ea9f8184ed0d4f8261d2af8c4ae8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563