Update not showing in dashboard

After weeks of procrastination I’m ready (though still very scared) to update to version 4.0. At the moment we’re using 3.7.1. Should have done it before, it might have stopped the hacking we got last weekend!

I’m sure previously my dashboard has offered to update for me, but now when I go to Updates it just says I have the latest version (3.7.1)

How can I make it update?

(I looked at how to do it manually, and that looks even more scary, but if it has to be done…)

Sue