Installation Error OJS

We use OJS version.
In the main page, on the top, we can read this message:

Warning : in_array() expects parameter 2 to be array, null given in /aplicativos/home/encuentr/public_html/lib/pkp/pages/workflow/ on line 373

And in the other hand, when we export the XML files with the Native xml plugin, we can read this in the xml itself :

Warning: DOMElement::setAttribute() expects parameter 2 to be string, array given in /aplicativos/home/encuentr/public_html/lib/pkp/plugins/importexport/native/filter/ on line 89


Any help? Are we having problems exporting the xml files because the installation of OJS is not done correctly?

Thak you very much