Not able to visualize PDF previews (not running OnlyOffice). Am I doing something wrong?

[xX-MrN0b0dy-Xx]

As title says, I am not running OnlyOffice, but I am still able to open and visualize .xlsx and .docx files with the embedded preview vistualizer.
Also, PDF files thumbnails are correctly created, but when i open a PDF file it only offer me to download it immediately, with no preview or possibility to browse it.

[xX-MrN0b0dy-Xx]

Sorry, my bad, everything is working. It was the machine I was using that had some bad settings.