Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6b1b02e27d9c4543ae56b0a248ed0573.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563