[LAU] Alsa not finding soundcard

Hello all, A friend of mine, who is mainly a Windows user and has limited knowledge of Linux, has two HP laptops running Archlinux. One of them works perfectly with an RME Octamic-XTC. The other doesn't seem to detect it as a sound card (it doesn't show up in aplay -l). On both the RME is recognised as an USB device (by lsusb). I'm trying to help him fix this (remotely). We compared kernel and alsa versions, they are the same. In fact the two Linux installations should be identical, both had a full update before I shipped to two laptops to him. What could be the problem on the second PC ? TIA, -- FA