Welcome to the site.

I split your reply to a previous post into a new topic for your machine. For us to best help you, please provide as much information as you can about your machine and what it exactly is or isn't doing. Also, slot machines have multiple DIP switch banks -- please be specific as to where the DIP switch you flipped was (is it on the processor board of the machine? is it on the bill validator?).
Based on what you've posted it sounds like you have an IGT S+ machine. The SET chip is certainly the first thing to try to see if your bill validator is enabled. If it isn't, it won't try to accept bills.
As one of our long-time members Stayouttadabunker wisely says, "the more you can tell us, the more we can tell you."