Is this plug-in still being developed?

I’m trying to start using it, but am already having problems with referencing the same source more than once.

For example, I reference it the first time and then try to reference it again using the following:

((ref:1))

However, it appears in the footnotes twice as 1. and 2.

Thanks for any insight or updates!

https://www.ads-software.com/extend/plugins/wp-footnotes/