Why does FrontPage 2003 hang when trying to open an old site stored on a local hard drive?

I am using Windows 11 Pro and when I open FrontPage it normally opens on the last local site used.

Today it gives a blank page.

When I try to open a site, it hangs – failing to respond.
Same thing happens when I try to save the blank page.

I tried restarting the computer – no change.

It worked fine for about four years on this machine with Windows 11 Pro. I am getting it to work with the workaround of using “open with” on an HTML file. When I do this, I do have access to the site, but this is a pain.

The files are stored on my local internal hard drive that works fine for all other storage. My system C: drive is an SSD. D: is data storage as well as programs I can put on it.

It freezes as soon as the Open dialog shows up. I’ve waited as long as half an hour. When I start FrontPage, I just get a blank page. If I go to Open Site on the menu, it hangs. If I go to Open, it hangs.

Here is a link to one of the files in the website: addbalance.com/usersguide/templates.htm The site has 11,774 Files, 349 Folders on my computer. It is more than 25 years old. The total size is ~770 Mb.

The computer is about four years old and working fine.

(EDIT: Additional information)
I also tried changing the properties to run in WindowsXP compatibility mode. This did not help.