HTML and PDF versions of articles downloaded and not shown in tha page

Hi to all.

I’ve just upgraded an OJS installation from 2.4.7 to 3.1.0

Operative system is Linux CentOS 5
PHP version is 5.5.32
MySQL version is 5.5.47

As far as now, migration of articles seems working well except for the following problem:
from both the “Issue view” (where articles are listed) and the “article view” (where abstract is shown), if i click on the “HTML” or “PDF” button both HTML and PDF version of the article are downloaded instead of shown in the page as it was in version 2.4.7

Maybe it’s useful to know that the version 2.4.7 is installed on the same server with exactly the same configuration of PHP, MySQL and Apache

I searched the forum for a similar problem but I got not results.

Thanks in advance for your help

I’ve found where the problem was:

after upgradind to 3.1.0 the plugins “HTML Article Galley” and “PDF.JS PDF Viewer” were disabled.

So, now this problem is solved