Mantra Theme pages not displaying

I installed version 2.2.1 of Mantra, and everything seemed to be going well until I tried to view the published pages. Only the home page displays. Every other page returns a 404. I have been thru all the settings I can think of, and I can’t figure it out. The Menu looks right, too. I’ve used other WordPress themes, so I’m not entirely new to WordPress but this has me totally baffled. Does anyone have a clue what I can do? Thanks!