I'm having the same problem.
Various pages on the LastPass site inform me:
You are running an old version of the LastPass plugin, version 4.2.0.
To upgrade to version 4.3.0, please click here.
I clicked the link, downloaded the exe, closed Chrome, and ran the exe.
But chrome still shows plugin ver 4.2.0
When I go to the Chrome store and search for LastPass, the button to install already says "Added to Chrome", so no option to update there.
Within chrome://extensions I enabled "developer mode" clicked "update now", but it does not update.
So I have tried 3 different update methods, and each fails.
How do you get the 4.3.0 update for Chrome?