Ensure the power cable is firmly plugged in to an outlet, and, if necessary, the outlet is switched on. Your Oster toaster may not work if the power cable has worked loose. Make sure the outlet is working by plugging in a lamp or other small appliances.
Verify the "Bread Carriage Lever" on the side of the toaster is pulled firmly down to start the heating process. If the lever does not engage properly, the toaster will not heat up and the bread will pop up.
Confirm the "Lighter/Darker" knob is set high enough to toast the bread. Turn the dial on the side of the toaster to a higher setting and repeat the toasting process.
Ensure the toaster is not set to "Warm" or "Defrost" mode. Press the "Toast" button prior to pulling the bread carriage lever to ensure your bread is toasted properly.
Contact Oster if these steps fail to resolve the problem. You may be entitled to a replacement if your toaster is within its warranty period. Oster can be reached at 800-334-0759 in the United States or 800-667-8623 in Canada.