Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/17ee6e4f67044e38b4d91ed16e3984d7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563