Collabora online not showing up when file is clicked

I have followed this instructions in this guide: but when I click on a file (odt, odp etc) I am taken to a page where the header/nav bar is present but that’s it. The page is otherwise blank.

Thee’s an A record for the sub-domain too.

Is there anything I should check? Where is the log file stored?

It often helps to add a hosts entry for the nextcloud and also the collabora machines

What do you mean?

For example, if you added these via

sudo nano /etc/hosts