You didn't say if you had updated this or if this was a fresh install, here is a link to a thread with the same error- https://bitcointalk.org/index.php?topic=5159481.0

It seems like their issue was down to trying to use an incorrect bitcoin core wallet dat in their electrum file section (I'm pretty sure) Have you ever had an install on this machine previously?

With the keen eye of TryNinja this seems to be your issue. Now I am just stuck wondering if you're a whale and truly have this large coin amount.