This article explains why Iptanus File Upload cannot be installed on a site hosted at WordPress.com.
WordPress.com is a widely used host for WordPress sites, personal and corporate alike.
Why the plugin cannot be activated
If your site is hosted at WordPress.com you will find that the plugin installs but will not activate. The message reads:
WordPress.com does not permit every plugin to run; their own explanation is here. Iptanus File Upload falls under “database and file-system altering plugins“.
What WordPress.com told us
We approached WordPress.com to see whether there was a way round it. There is not: they do not allow files to be uploaded through plugins at all. Their answer:
If customers need to upload any specific file to any directory on their sites, they can contact us so we can check if the files are safe to upload, and do it on their behalf.
Global Happiness Engineer, Automattic
Where that leaves the plugin
So Iptanus File Upload cannot run on a site hosted at WordPress.com, in either the free or the Professional version. It works normally on self-hosted WordPress, wherever that is hosted.
We are sorry about it. If you would like more information, please contact us.
The Iptanus team

Good morning,
I am getting several error messages which I shall forward.
First though, can you allow .webm video files please?Peter
Hi, to allow webm extensions, just set Allowed File Extensions in the shortcode like this: *.*, *.webm
Regards
Nickolas