Lightroom is unable to authenticate

Attempting to publish from Lightroom using 5.2.1 plug-in.
This plug-in’s post-processing task did not finish successfully.
Unable to perform action: uploadRendition

Unable to authenticate

Check that:

the main part of the site url and the api url match exactly. For example, if your site url uses https, make sure that the api url does as well.

The api key in Backlight and Lightroom match

I remembered where to enter both data fields. That is the challenge for those of us that don’t spend a lot of time with Backlight, figuring where settings or data are entered.