There is usually ample adjustment, so if you have used all of that, I would take a look at how the track is fastened to the opener, to make sure that the opener hasn't shifted toward the door. I think that you will find that it has, and if so, lenghten your chain back out, loosen the clamps or whatever hold the track to the opener, slide the opener back, tighten the clamps, and adjust the chain.
Make sure when you are checking your slack in the chain that you disconnect the door from the opener first. Depending on how much the down limit control is adjusted, it will often put tension on the opener rail which will put slack in the chain. When you disconnect the door, there should be no stress on the opener rail and you can get a true idea of how much slack. What kind of opener do you have and how old? Most of the modern openers have rails that bolt solidly to the opener head with no adjustment at that end.