Analytics Last Update time has nothing to do with whether you are getting live data from your site.
It's often that people will see the phrase 'Analytics Last Update time' in the upper right of their heatmap and notice that the last update was a month ago. Then they look at the trends and find that there is live data. Wtf.
Well, Analytics Last Update time is the last time there was a change to what points are being displayed in the trend widgets. Typically this value only updates if 75F support updates the Custom widgets with new points.