Replacing LNB

I was getting zeros on every other transmitter on satellites 99 and 103 and not getting most HD channels.  I was told that it could be a bad connection and so I by-passed all connections with new wire and that did not make a difference,  I was then told it was probably the LNB so I bought a new one on ebay.  Assuming that the LNB is good - I can't get it to be recognized by the receiver.  I have an older model dish (AT9 5 LNB KA/KU) and I replaced the LNB with a SL3K4NR1-03.  Is this LNB compatible?  What dish should I select when doing the dish setup?  Is there anything else I should be doing?