Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a8f2d1522060d81a7d132a5be0db3295.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563