Why can't I view PDF on my Android tablet?

When I try to view a PDF on an Android tablet, the activity screen appears as shown in the attached image, and the PDF cannot be viewed.
How can I view it?
It was available for viewing until two weeks ago.
It can be viewed easily using a PC (Mac&Win) browser or an iPad app.
Please help me.
Thank you.

@Knoby hey and welcome to the community-forums of nextcloud.

I’m afraid your thread is missing any information. How could we help if nobody would know what you are running, where, which versions, etc.

You must not delete the underlaying template. We don’t want to torture our users here but in most cases it would give us some worthy informations about your system(s) … and make it easier to help you.