3.6 404 error

Hello, I have installed the new ci 3.1.6. My login and main page loads fine but when I click a link I get a 404 error. The pages were loading fine in 3.1.5. I am using routers and controllers to load pages.

There are zero changes in 3.1.6 that could cause this. The problem is in something else you did (or didn't do) on your new setup.