Hi,
Please check the following -
- 301 redirects - Once the domain name was changed have you placed 301 redirects. Domain A >> 301 redirect >> Domain B.
- Page level redirects also need to be in place. For example - domainA.com/Page1 >> 301 Redirect >> domainB.com/Page2
- Check for robots.txt file. You might be blocking the search engines.
- Check for SEO elements such as Page Title, Metas etc. If you have not retained these elements, you might see a drop in rankings.
- Check for no index and no follow. Maybe you have placed these tags on all the pages and hence the drop
- Check the XML sitemap, ensure that you have submitted the new URLs via the XML sitemap
- Check if you have made major modifications to the content. If you have changed the content by a great extent, then it's a possibility that the old pages had better content from an SEO perspective as opposed to the existing content.
- Check if you specified the correct GEO in Google WMT
- If you have done all of the above, then check your backlinks, maybe your domain transition coincided with an algorithmic penalty (either manual or automated). Check WMT messages for details.
Hope this helps.
Regards,
Sajeet