A new trend in adware and unwanted program purveyors is to install protection software that makes it more difficult for Windows users to run security programs and clean infections. This was seen with the SmartService rootkit that blocked AV software from running and now with a protection program called CertLock. CertLock disallows a security vendor’s certificate on the affected computer so that Windows does not allow the program to run. When a user tries to run the programs, they are greeted with an alert that states that the publisher has been blocked from running.
Source: https://www.bleepingcomputer.com/news/security/certlock-trojan-blocks-security-programs-by-disallowing-their-certificates/