Auto update not working

Have CIS Premium on my XP desktop - trialling and I cannot get it to auto update even though I have set it to do that in Scanner settings > Real time scanning > Automatically update virus databases.

I find most of the time I have to update manually from More > Check for updates or Summary > start scan s and then it proceeds to download definition updates.

Am I doing something wrong or is it a feature of Premium not to auto update?

What happens when you run the diagnostics?