If your store won't display (or you get a 404) after you have clicked the [Update Products and Settings] button, here are some steps to help troubleshoot the problem. After you perform each step below, be sure to check to see if your store is displaying properly.
1. Turn OFF any caching plugins.
This is essential and will save you hours of wasted time in the debugging process. Trust me. I've been there...
2. Make sure there is only 1 WordPress Page for your store.
3. Make sure that your Store page slug matches the slug in your Advanced Store Settings.
4. Make sure your Store page is set to Public and is Published.
5. Make sure your Settings > Reading settings are configured correctly.
This section does not control whether your store appears on the front page of your site anymore. If you want your store to appear on the front page of your site, follow these directions
If you have modified your Reading settings, you should reset those to these settings: