You will not be credited for that backlink
- Google and Bing will only credit for backlinks to indexable pages
- Google and Bing can not discover backlinks on pages that require authentication
Visible PageRank is obsolete because...
Google no longer updates pagerank, the last pagerank update we received was back in 2013.
PR / DA and so on
Thought I would add a little more about PR and DA because you seem to be focused on PR and DA which is the number one problem for failing to increase rankings when not fully informed. Google and Bing, no longer reward just on PR and DA the same way they used too. PR and 3 Party DA ratings are only good if the content is relevant.
It's not all about high numbers, its about relevancy, for example Facebook has a massive MOZ DA but passes very little. A 6 PR site about cars will pass very little to a site about cats, and enough of these useless links will actually work in a negative effect.
Also, the actual page contents matters too, if the page your receiving the link from is not on topic, thin and low value, or even duplicate content it will reward less than a unique page with great content. Looking at DA and PR is pointless, you want any DA/PR from relevant quality sites with unique page content.