Can't Add a New Gallery

This wonderful plug in has worked for me for years. (site: https://romaninukraine.com)

Recently, I couldn’t add a new gallery. I already have 78 separate galleries and they continue to work. I just can’t add a new one.

I type the name of the gallery and see that a folder has been created with that name in /wp-content/gallery, but it doesn’t appear on list under “manage galleries” and it’s not in the drop-down box for “upload images.”

I thought this might be a 2.0 problem, so I reverted to version 1.9.13 using these instruction: https://www.nextgen-gallery.com/how-to-rollback-a-version/

But I’m still getting the same problem. I’m stumped. Any ideas on what the problem may be or how to trouble shoot?

Thanks.

https://www.ads-software.com/plugins/nextgen-gallery/