Work on quality back links. The page rank updates don't happen everyday so if your site is new than that would be the reason.
Google calculates pr of websites in regular intervals.If your blog isnt old enough you won't get.i think its three months the time frame.
Page rank does not depend on the number of visitors. It depends on the back links your site is able to generate from higher ranked websites/blogs. Try to network your blog with well ranked blogs to be able to successfully get PR juice from them! Regards, RightMan
More backlinks, less links that coming out of your site. Maybe the competition is better, or maybe Google doesn't like blogspot anymore.