Kaltura MediaSpace will give the error message "User was not found or is not eligible, choose a valid one" when trying to add a user that has not logged at least once to a media item as a collaborator (co-editor, co-publisher, etc.) or a channel at least once.
In order to add a user to a channel in Kaltura MediaSpace or add a user as a collaborator, the user must have logged in at least once to Kaltura MediaSpace. If the user has not logged in at least once, you will see the following error when trying to add them: "User was not found or is not eligible, choose a valid one."
If you see this, please contact the user you are trying to add and ask them to launch Chrome or Firefox and go to Kaltura MediaSpace: mediaspace.wisc.edu to login. If they need more information on how to log in to MediaSpace please refer them to Kaltura - How to Log in to Kaltura MediaSpace (UW-Madison) .