For a long time now the scrapebox backlink checker has used Alexa data. Alexa all of a sudden started limiting the data from 1000 backlinks to now only 5 backlinks, if you want more, you have to pay for Alexa Pro.
So Scrapebox transitioned to using MOZ API, similar to the Page Authority addon. In the video below I cover how to setup an API key, how to setup the addon and how to use it.
The major upside here is that MOZ data is considerably better and much fresher then Alexas. Also it will pull in your accounts from the page Authority addon , if you have any setup in there.