1. If you're running Media Deduper on a development site that's password-protected using HTTP basic authentication, you'll need to use this plugin to make WP cron work: https://wordpress.org/plugins/wp-cron-http-auth/
2. If you have lots of large image files, there's a setting you can enable.
From Settings in your WordPress Admin, navigate to Media Deduper Pro and select the option to Run Partial Hashes.
This will tell MDD to analyze only the first 5 MB of each uploaded file instead of whole files, which can speed up the indexing process.