You mean using the link from the Links page? https://mobilit.belgium.be/en
It seems to be still at the same place, the "My vehicle, my plate" link on that page
Previously linking directly to the right page did not work, but maybe now it does?
Testing: https://www.mobilit.fgov.be/WebdivPub_FR/DivConsStatut.html
Does this work for you? If so I can replace the link by this one.