Unable to configure NTP on HP 1910 / a5500 / 1920 etc

HI! Im having troubles configuring NTP protocol on, for example, hp 1910 using comware 5.20.99. I follow this exact instructions

http://h20564.www2.hpe.com/hpsc/doc/public/display?docId=mmr_kc-0122003 

[SWCORE]ntp-service authentication enable
[SWCORE]ntp-service authentication-keyid 24 authentication-mode md5 aNiceKey
[SWCORE]ntp-service reliable authentication-keyid 24

Then i configure from the web interface any other switch as the tutorial says, and nothing happens. Maybe i'm missing something. Please help!

Thanks in advance