No crank no start

I stopped at the gas station pump to get gas. When I tried to start the ignition, it would not crank. There was a definite electrical click when I first tried to start at the gas pump, but would not start. This is the first time this has happened since I purchased about it two weeks ago. It has happened abruptly for no apparent reason without any warning. When I have had this problem before with other vehicles, it was always the battery or bad connection to the battery. I checked the connection to the battery and discovered the negative battery cable was the wrong size, too large for the terminal to make a tight connection. I walked across the street and purchased a new brass terminal cable that fit proper and tight, but go the same result. I then purchased a battery tester for amperage and the meter tested in the okay range indicating the battery was good. Several consumers tried to jump start it unsuccessfully. I called AAA Roadside Assistance for a tow. An AAA Roadside Assistant arrived in a AAA pickup truck and tried to jump start it, connected the positive to the negative and the negative to the positive battery terminals causing a large blast of sparks to shoot from the battery terminal. He jumped back quickly from the battery and shouted out something. I told him he did not connected the terminals correctly. He replied he thought the gold cable was the positive. I told him the + and - signs are clearly engraved on the battery and the positive battery cable also has a + engraved on it. He did not look for the correct terminal to connect to and was not a tow truck. I told him that what did can cause damage to the electrical system, starter, solenoid, alternator and other parts. I was concerned that he may have caused damage to parts of the car and he was not a tow truck that I requested. So, I did not want to continue with him. I called AAA again and requested a tow truck. He left and a tow truck came and towed it home. When I tested the interior fuse box, none of the fuses light up with a test light. Now, when I try to start it, it does not click as it did before. Only the dashboard lights go on and off. The dashboard lights go on and off. The security key light blinks, rather than a steady on, for a few seconds and goes off. I have never had this problem before and do not know what the problem is nor the solution. There are a number of possibilities, such as blown fuses, relays, starter solenoid connection, wiring, starter malfunction, security system may have disabled the started by activating the immobilizer, the neutral safety switch, etc. Can one, two or more of you CarPros please help diagnose the actual problem with a solution?