Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6c503b259a3f20df5b6b1a428407f5da.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563