Comment 3 for bug 248862

Note that this problem is probably not linked to UPnP or the router. This is a port binding error and not a port mapping one. Therefore, libtorrent reports that it is unable to open a port on your computer. This usually means that the port is already taken by another application.

Do you confirm that qBittorrent is actually working properly (i.e downloading) although you get this error on startup? Or do you have to save the program preferences again in order to make it operate properly? This will help identify the problem.