PDF preview not opening inside app

Self hosted.

The PDF previews for invoices etc are not visible in the preview window. So if I customise the invoice, I cannot know how it looks. It only shows me a blue colour ‘Open’ button in the preview window. Once that is clicked, it asks to download the PDF.
I would like the PDF previews to be shown so the changes or customisations can be immediately viewable.
Please guide.

I was using chrome. Had to switch the setting of not downloading files for preview.
Now the previews are showing.

Glad to hear it’s working, thanks for sharing the solution!