FYI.
I figured it out - It was to do with the Firmware Rev 5.0 - It only allows 300,000 data points not 1,000,000 in the data log trend set up. I have 67 tags in my model so to get trending on 1 tag/pen for 24 hrs I had to change my sample update to 20 seconds.
I changed the data storage path to "default" as I couldn't get it to store to the USB stick but we now have historic trending.
H.M.