Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5a688551e3c6d96ba8a0d4cb8e50431d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563