Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f6c2b98c2c64db4699257c6574f4acdf.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563