Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0a4875c25fe1a25db40b4264f30d053e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563