I'm trying to imagine the screen you are looking at when you see enrolled students with blank entries. Hopefully, you are you looking at the page triggered when you click on the specific journal and then the "View X journal entries" link?

If it is the latter, you SHOULD see student journals (if they are writing them). Click on the log button at the top of the journal to see if your students are visiting the page. If they are viewing the journal but not "adding" journals, then something is wrong. Are you sure the journal is open for editing? You might need to set a longer date on the journal by "updating the journal" (another link on the individual journal page) and extending the "close" date.

Sorry to be slow in responding to this question. If you are curious about the group interface for looking at journals group by group, I don't think that the work is complete on that yet. I'd keep the journal set to "no groups" until the coding is finished.