Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8b6b0d892356915cda1f782e8652ba51.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563