hp-plugin fails

[Pierre Frenkiel <pierre.frenkiel@gmail.com>]

hi,

when I run hp-plugin on my laptop (debian/stretch), it says
   driver plugin for HPLIP 3.16.11 already installed ...
   (the hplip package version is 3.16.11)

if I do that on my desktop (debian/buster), I get:
   error: Unable to open /data/home/frenkiel/.hplip/hp-plugin.lock lock file.
   (the hplip package version is 3.18.12)

sudo hp-plugin gives:
   warning: It is not recommended to run 'hp-plugin' in a root mode.


googling didn't give me any useful information...

I tried also:
   hp-diagnose_plugin
    which gives: failed to install plugin

   sudo hp-diagnose_plugin ==>
      warning: It is not recommended to run 'hp-plugin' in a root mode.
      Checking for network connection...
      Downloading plug-in from:
      Downloading plug-in: [\
   but the download runs forever, with 0% downloaded

Can anybody suggest a fix?

best regards,
--
Pierre Frenkiel