Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/75cc7abb2ce7d531f3e8ac6b64571450.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563