[Plugin: WordPress SEO by Yoast] Author names are blank

I have experiencing an odd problem with this plugin:

The author name return blank – I have tested the WordPress function:
get_author_name() and it is returning empty when I have WordPress SEO plugin enabled.

E.g: https://www.hostliketoast.com/2011/07/what-is-cloud-hosting-compared-shared-dedicated-hosting/
on the byline there are 2 lines – the first one is a hard-coded workaround, and the second is using Thesis by-line functions. The problem is not thesis because I have tested the WordPress function (above) that Thesis also uses.

When I disable the WordPress SEO plugin it works as expected.

I originally had “Disable the author archives” selected and then I decided to add another user. When I did this, I went back into WP SEO and unchecked this box in the hope that this would resolve. Alas no.

I have disabled other plugins (like W3TC) and added new users with the WordPress SEO plugin enabled/disabled and nothing seems to get this author name to display.

Any ideas?