Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b99b6f583898c5d2a1d6542ee3df8304.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563