From what I know about Kaltura (which is just a little), it's a commercial video streaming service. I would think the video that is uploaded isn't uploaded to your Moodle, but to a Kaltura server/service somewhere on the net.
The error about invalid URL sounds like the plugin hasn't been configured ... that's a guess ... like I said, don't use Kaltura.
Is this the addon?
https://moodle.org/plugins/pluginversions.php?id=447
If so, that is a 'package' that requires placing the contents of the unzipped plugin locally to put the kaltura software into filter, lib, local, and mod of Moodle code. See pic for an idea.
Also see:
https://knowledge.kaltura.com/page/kaltura-products-and-services-documentation#block4moodle
There are also some bugs ... dunno if one of them is like yours, but check it out:
https://github.com/kaltura/moodle_plugin/issues
'spirit of sharing', Ken
