The error message typically appears if you bought the wrong update.
From the Activation Manager screenshot I think you already own and have activated Wavelab Elements 13 previously, because you did this update already some time ago. Login to your Steinberg online profile and check the activation there, it shows a date.
So assuming you already have Wavelab Elements 13 the error message is correct, because you are trying to update from Wavelab Elements 12 and you do not have it anymore (even if you can still run it), it has been updated already.
Well I tried another permutation of how to do this:
Uninstalled Wavelab Elements 13
Installed Wavelab 12
Re-installed Wavelab 13
Now it works.
Honestly this should not be as difficult as it was. The instructions are misleading, there are 2 different programs (licensing and downloading/installing) and I only got it working by taking a “drunkard’s walk” around the problem.