No electrical power, no crank, no start

About two weeks ago I replaced the starter in my car. After I replaced the starter everything worked fine. Two weeks later I got to get in my car to start it turn the key in the ignition and nothing happens; no lights come on, no clicking sound, no nothing. So I’m trying to figure out what is wrong with my car so I can pay to get it fixed. It’s not the battery either because I took the battery to O’Reilly‘s and they charge the battery they did say however though the battery was dead whenever I brought. It in so I’m trying to figure out if it’s the alternator or ignition switch or what?