Help on native xml import of articles

I have a few problems in using the nativa xml import file and I wonder if I can get some help from you. I am trying to upload a series of article in Italian. This is what happens:

  1. content is uploaded and displayed online in the public site
  2. some information needs fine tuning, so I edit metadata
  3. some metadata are empty even if displayed (title for example) but I cannot add or edit metadata (even adding the title in the blank space works) and I receive the following error message:

Errors occurred processing this form

Please enter the title of your article. (Italiano)

Please enter a language.

Please enter a discipline.

Please enter a keyword.

I have since used a different tag (<“en_US”> instead of <“it_IT">) and I can now add/edit contents, but the DOI is still not imported and I need to add it manually.

I would like to know exactly how to import correctly into the site.
Thanks anyone who can help me.