Recent versions of Internet Explorer may block installation of the DVR plugin software due to it being published by an unknown source. This isn't a security risk, it's simply because the DVR manufacturer isn't known to Microsoft and has not been white-listed as safe. To work around this:
- Click the cog icon (top left of the window), or Tools
- Click Internet Options, Security Tab
- Select Trusted Sites, set the security level to Low
- Click Sites, un-tick "Require server verification..." then add the address of the device to the list.
- Close this window, then click OK.
- Reload the page, the plugin should now install.