I did the 2.xx to3.xx upgrade as described and it says it completed OK, BUT! Once I log into the admin area and try to select any functions, like setup / config, I get a page not found error, when those pages DO exists on the server. All was uploaded in binary. If I login, I see all my users, however if I click any of the links on the left menu bar, I get a Page Not Found Error. Customers ARE able to log in... When I try to use my old signup links I get raw text pages as if css is not working... (Scratching head...)
Whoops! Looks like I left the https:// entry in setup when the server has no SSL cert installed. Duh! I'll install a Cheap Turbo SSL Certificate quickly and I'll bet that fixes the issue. Update: Yes, that fixed the problem.