Disqus is a better comment system for WordPress.
Deactivate the Akismet extension if you are using Disqus.
Enable Akismet on your disqus.com settings page.
To keep all the WordPress comments made before adding Disqus, click "Export comments" in
WordPress > Comments > Disqus > Advanced options > Export comments to Disqus
This adds to Disqus all your WordPress comments made before adding the Disqus extension.
That is done automatically.
You should never need to click "Sync comments" in
WordPress > Comments > Disqus > Advanced options > Sync Disqus with WordPress