[Q] LG G3 knock code screen lock method disabled after installing certificate topic

Hello. After I installed this certificate (lrz.de/services/netz/mobil/vpn/anyconnect/rootcert.crt) I am no longer to use knock code as a screen lock method. I found out that the name of the certificate is Deutsche Telekom Root CA 2 and disabled it from the trusted credentials menu, but I am still not able to select knock code in the lock screen -> select lock; the options Swipe and Knock Code are white and cannot be selected (It says disabled by administrator, encryption policy or credential storage)
Any help would be much appreciated