I don't believe 'adapt-footer' has actually been made authoring tool compatible. Although it has a properties.schema, if you look inside it, it's pretty much empty.

I see you've already logged a ticket with the owner of that plugin, which was my recommended next step!

You might try https://github.com/cgkineo/adapt-footer - not sure it's as full featured as the above but it definitely works with the authoring tool... switch to the release/v5 branch if you need the FW v5 compatible version.