I spent about an hour yesterday to find the solution for Disqus to work correctly on my newly imported Blogger blog on WordPress. Here is the problem and the solution to that problem.
The Problem –
I had recently imported my blog from Blogger to my self hosted WordPress site. I had installed Disqus Plugin correctly, but I was not able to see past comments in the Comments section of my WordPress site. I tried to sync all the comments manually for multiple times, but I failed to see the comments. The comments were not visible in the Comments section and also below the individual blog posts on my site. Those comments were safe on Disqus site though. I was frustrated while going through the settings and options in Disqus, where I found the exact problem.
The problem was the URL. Blogger blog posts use numbers in their URL by default. When I imported my blog on WordPress, I changed my blog URLs (Permalinks) to Post Name. So the blog posts on my site now had different URLs. I was not able to see Disqus comments on a particular blog post, simply because comments were not made on that URL. The URL of that post was different when the comments made on it.
The Solution –
There is a solution to this problem in Disqus settings. Go to disqus.com and open Discussions section of your site. Click on Tools. As I have not changed the domain name of my site and only the URLs of my blog post have been changed, I am using URL mapper. You can use Domain Migration Wizard, if you have changed the domain name of your site. To upload a URL map, click Start URL Mapper. Click on the link given on that page to download a CSV file of URLs listed on Disqus. Disqus will send you an email containing the CSV file. Download the CSV file from your email and open it using a simple text editor.
The file contains the list of past and current URLs on your site. You need to edit this file. If any of your blog post previously do not have any comments, you can just skip and delete that URL. Write all the remaining URLs in the given format and then save the file. I will explain this with an example. Suppose the old URL of my blog post is –
I will enter a comma just at the end of that URL, then space, and then I will paste the new URL of the same post. The format will look like this,
Come to the Disqus website on URL Mapper tool again. Upload the newly saved CSV file and confirm. All the Disqus comments on old URL will get mapped to the new one.
For more help – Moving from Blogger to WordPress.