I am trying to attach a file in the "Send Fax" wizard of HP Device Manager (HPLIP 3.20.6).
In the window called "Select Files to Send", I click on the "Add…" button, and I get the error
Unable to create io-slave. Can not create socket for launching io-slave for protocol 'file'.
This has nothing to do with the specific location of the file I want to add, because I get the error before I can choose location.
Aside from this, the fax wizard works as expected.