I'm not sure which, but in trying this plugin out on one of my video sites, I noticed that on posts where I use Featured Video Plus to embed a video, the Floating Social Bar was hidden behind the video, so it was hidden at the normal page position, but if you scrolled down to read more content, the FSB would appear, as normal.
When I edited the post to add a break at the top, above the video, that caused the FSB to have enough space to display, but for some reason, it also caused the author to disappear from the post and the post listings in the admin area. The author is still displayed on the actual post, but it's blank in the admin area and in the post edit page itself.
Using the Co-Authors Plus plugin for that.
The other site I'm using doesn't have either Featured Video Plus or Co-Authors Plus installed, but I was planning on adding Co-Authors Plus at some point in the future.
I think the issue is somewhere in Co-Authors Plus, but I'm still poking around