HTML file does not show up Viewer Pane on new computer

I'm transferring HTML files (they were e-mails exported from Thunderbird) to my new computer (a Windows 10). The files will not appear on the viewer pane on the new computer although they appear on the older computer (also a windows 10). Is there a setting that will help? The viewer pane really comes in handy for quickly checking these thousands of html files.
Thank you!

The viewer pane uses Internet Explorer currently. It may not be available on the new machine.

(We will be moving to Edge in the future.)

Hi Leo,
I'm able to see it under Directory Opus on the older laptop. I'm not using Internet Explorer. I look forward to this feature being updated. On the new computer, other files such as pdf's show up on the viewer pane, but not the HTML files. Thank you.
I love Directory Opus and have been using it for years. It's so reliable. I've never lost a file which is more than I can say for the Mac computer.
Melissa

If you run IE on that machine, does it work?

The viewer pane always uses IE (at the moment), regardless of which browser you use in general. (Until the new Edge, IE was still the only browser that it was possible to use in other software.)

I will try that and report back as my new computer has crashed. . .