Each Cubase license upgrade replaces the earlier version. You may need to download and install the most recent driver the for the USB eLicenser in order to see the newer license. You should see only the highest-numbered license (i.e. Cubase 10) but that will allow you to continue running Cubase 4 as well as all other versions.

So in other words, your Cubase 4 license hasn’t been wiped, it’s been replaced by the Cubase 10 license, which includes the right to run all earlier versions of Cubase, including Cubase 4.

Thanks very much for your reply. Unfortunately, the USB licenser holding my Cubase Pro 10 license, isn’t working with Cubase 4.5
This is really frustrating.
I have downloaded again the e-licenser installer from Steinberg, for Win XP (that’s what I’m running Cubase 4.5 on), but when I click on the .exe file to install it, nothing happens…

Now even when I log into my “My Steinberg” account, it only shows one USB licenser for my Wavelab. It doesn’t even show my Cubase licenser…
WTF is going on???

Oh dear – Windows XP? The last eLicenser for Windows XP was version … on the eLicenser website, click “Downloads for Older Operating Systems”. Make sure that’s the version you’re running, and if that doesn’t work, you’ll have to log a support ticket with Steinberg (this is a user-to-user forum).