new design / layout has removed my site from google

[Romerz]

We've recently updated one of our eCommerce websites to something a bit more modern (opencart). This obviously means that all of the previous URLs are now defunct.

I have submitted the new sitemap via the webmaster tools, however my entire domain now no longer shows up on google, bing or yahoo.

When I check the advanced index status, it shows

Total Indexed: 1571
Ever crawled: 5813
Not Selected: 12,131 <--
Blocked by robots: 0

I'm assuming that I have missed something out?

[Robert Charlton]

Have you checked existing backlinks to your previous urls, and did you 301 redirect the urls which did have backlinks to corresponding urls on the new site?

I have submitted the new sitemap via the webmaster tools, however my entire domain now no longer shows up on google, bing or yahoo.

Sitemaps are not a substitute for 301 redirects. It sounds like you need to put some proper redirects in place as quickly as possible... and then, if possible, get some of the old sites that had linked to you to change their links to the new urls.

[HuskyPup]

How long ago did you do this?

[Romerz]

I thought that may have been the case, however I would say that 95% of our backlinks point towards our main .com domain rather than specific pages.

[Romerz]

I updated to the new system about 10 days ago.

[jonathantaioba]

Have you checked noindex tag on your pages?
Are you sure that Googlebot can crawl your pages? Check your robotx.txt file.

And it's really important to have your old pages redirecting 301 to your corresponding pages in your new webiste.

[Sgt_Kickaxe]

This obviously means that all of the previous URLs are now defunct.

This is exactly what you should expect to have happen if you suddenly delete everything the search engines know about your site(urls). Creating a new sitemap will help in ranking the new urls but they are first time urls as far as search is concerned, worse they may even be considered duplicate since search has seen the same content on other pages from your site.

You've got to redirect the old urls to the new urls, assuming it has the same content, on a page by page basis using a 301 permanent redirect for any of the trust/links from old pages to flow to the new pages. A sitemap doesn't help carry value from old url to new.

Tip: At this point, when you've completed assigning a 301 redirect from every old url to its new home, leave both versions, old and new, in the sitemap long enough for search to fully find the new and remove the old from their index. You can remove the old pages from the sitemap at a later date, in a month or two, and not see any problems(assuming you get the 301 redirects correct).

edit: sorry, I just noticed that Robert Charleston mentioned 301s in his response above. Doooooo eeeeeet!