Error when importing with Private files

Hi

I get the following error after I have started the import.

The error log says:
InvalidArgumentException: The URI 'private://feeds/importfile.csv' is invalid. You must use a valid URI scheme. Use base: for a path, e.g., to a Drupal file that needs the base path. Do not use this for internal paths controlled by Drupal. in Drupal\Core\Utility\UnroutedUrlAssembler->assemble() (line 65 of /var/www/www.domain.com/www/core/lib/Drupal/Core/Utility/UnroutedUrlAssembler.php).

All data is being imported and the file is saved to the private folder - I am able to run the import again with no errors.
But on first import with file upload this error returns a very big red box with lots of text :-)

Start of the error page is:

An AJAX HTTP error occurred.
HTTP Result Code: 200
Debugging information follows.
Path: /batch?id=21&op=do_nojs&op=do
StatusText: OK
ResponseText: 
Page name | Site name
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(Removed. Here is placed the content on the front page as text)
{"path":{"baseUrl":"\/","scriptPath":null,"pathPrefix":"","currentPath":"node\/2","currentPathIsAdmin":false,"isFront":true,"currentLa... and much more

Any one have any ideas to what I should try?
Thanks.