with a single cable from LNBF to your reciever, using DISEQC to select Port 1 for
C band and port 2 for Ku band is the only way it will work.
The receiver must electronically pick which band to use.
With the Jumper installed at the LNBF, change your reciever to use Port 2 for Ku band.
I don't know what the screens look like on your receivers - but for a Fortec model there is a "PORT" setting. Use port 1 for C band and port 2 for Ku