Should Cubase 8 work with elicenser dongle even if dongle registered before?

I sold a copy of Cubase 8 Pro on ebay with my dongle which already contains the license.
The person who bought my copy has messaged me saying they can’t use the e-licenser- there is an error message saying it’s already registered to someone else (i.e. me).
My question is, do they need to register the dongle? Shouldn’t it just work when plugged into their machine once they’ve installed the Cubase DVD’s?

They don’t need to register it for it work, but you absolutely MUST unregister it for them to be considered the new owner of your eLicenser, otherwise they wont be able to receive official tech support and Steinberg wont be able to restore the licenses if he loses/breaks the dongle.

Go to your MySteinberg and unregister it. The link to unregister it can be found in your list of eLicensers.