Widget position is never saved

The feature/bury functionality works for me, but the widget never displays because it won’t “stick” to any location in the widget manager. When I try to place it in a widget position the “busy” wheel just spins forever and the widget never takes its place there. To make sure it wasn’t a conflict with another plugin or theme I tried it on a separate test site with Twenty Fourteen and no other plugins installed. Same result.

I’ve never seen this happen before, so I’m stumped. I’m using Firefox, but I also tested with Chrome and got the same result.

https://www.ads-software.com/plugins/feature-comments/