Hi Nicolas,
I have put the instructions for updating the Bkool Pro here: Bkool smartpro black - no connect zwift - #19 by Sandy_Thomson
I’m not sure if they work for the Bkool Classic, but I think the instructions in Spanish that I got mine from mention using a cable so it might be worth trying those: AFECTADOS POR RODILLO BKOOL | Página 80 | ForoMTB.com