GM changed from the old Homelink (which worked with just about all of them) to Lear, and now it seems to work with hardly any of them! Call that Lear customer service # and see if your opener unit is compatible (mine isn't, and many others' aren't either) - if it isn't, they will sell you a "transponder adapter" thingy that will supposedly make it work?
It's a sore subject with a lot of us unfortunately...I refused to pay the extra cost and just use the transponder that the garage door came with. GM probably shaved a few pennies by going to a cheaper system, and now it seems like it sucks...(and this coming from a lifelong GM fan)