We know that when you migrate from HTTP to HTTPS, Google does an extra special effort to pick up on the migration faster and pass all the signals possible as soon as they can. But we also know that Google has completely killed off toolbar PageRank.
So when one webmaster asked why their Toolbar PageRank hasn't transferred over during an HTTPS migration, John Mueller of Google responded on Twitter because "we haven't updated Toolbar Pagerank in years, so that would be normal."
@diwakarmudaliar We haven't updated Toolbar Pagerank in years, so that would be normal.
— John Mueller (@JohnMu) April 5, 2016
Real PageRank will flow from your HTTP to HTTPS pages, but there is no such thing as Toolbar PageRank anymore.
Forum discussion at Twitter.