There are some application and services which are responsible for removing any dev-certs added to keep a specific certificate always as the first priority (maybe - like an organization's certificate). Look for these app or services on your computer. I've had installed one for my previous job and I didn't know that this app is removing them.
How to find the app or process: Install Procmon from here. Then add a filter on Path which Contains Microsoft\SystemCertificates\My\Certificates. Then look for the reason in the process Name column. find it's exe and remove it from your computer (inside programs and features).
