You may try to repeat the media detection, but even if it does succeed the second time, you may experience problems later in the installation.
Tzemreḍ ad tɛerḍeḍ allus n tifin n umidyat, maca ma yella ur teddi ara tikkelt-a, tzemreḍ ad d-temlileḍ d wuguren ticki deg usebded.