you cannot use any regular spliter. make sure all you cable is without one. hmmm... sounds like you have a different LNB, try to use a
diseqc switch ( you may buy one from ebay abount $5) connect to both H and L (outlet 1 and 2 of LNB) to diseqc switch LNB1 and LNB2 with 2 shorter cable then to your 1st cable directly to your receiver, so your receiver will scan both H and L. do the same on the 2nd cable with outlet 3 and 4 of LNB to another diseqc switch later if you like. good luck
i assume your lnb has 2H and 2L outlets, 1 and 3 are H, 2and 4 are L.