I'm going to take a guess: rather than selecting a particular inbox, click the line labeled "inbox" at the top of the section (it has a disclosure triangle to the left), and see if you get the combined view of all of the inboxes.
If you want to see the specific inboxes, you can click on the disclosure triangle to the left of the "inbox" line to reveal those, then click on a specific inbox of interest. The triangle will go from point-right to point-down. Or click on the disclosure triangle to get the inboxes consoldiated/hidden. The triangle will go from point-down to point-right.