Not having so much information about the context of your issue (ez publish version, custom design and content classes or not, etc.. ) i'd advise to spot the template used for displaying the blog posts, and search for a variable called $limit or something similar. This variable is most likely used to limit the amount of blog posts fetched ( in a 'fetch' function in the template ), and conditions pagination as well.
Let us know how it goes, Cheers,
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Nicolas Pastorino
Director Community - eZ
Member of the Community Project Board
