Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/271907e2a7f3f6810ebe4a0bf8e68c01.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563