Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/19fde6f60b17c5ef7f092ac8bf4c7a47.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563