Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/64a3169d66c97d11ebd7d853c3698c12.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563