Go to ... https://www.steinberg.net/en/mysteinberg.html
and log in. Choose the Tab "eLicensers" under these 3 big red buttons. Click on the right side on the show details triangle ... scroll down to the end of the list of the elicensers content ... there is a gray link "Remove USB eLicenser from Account" ...
But .. this is not possible for Software eLicensers. If it is an SeL ... Steinberg Support must help.
Halion 5 & Friends, Mac Mini i5 late 2012, 16GB, OS X 10.8.5, M-Audio 1814 FW, M-Audio C140, M-Box Micro, Pro Tools 10, Pro Tools 11, Reason 7, Logic Pro X