1991 BMW 325 1991 BMW 325ix won't start after jump

I have a 1991 BMW 325ix with roughly 160k miles on it. I left the lights on overnight about 2 weeks ago. We tried to jump start the car, but the engine wouldn't even turn or crank. We removed the battery and took it to autozone to get it tested. It tested good. We recharged the battery indoors for over 24 hours and it held a good charge. We put it back in the car and tried to start it. Again the engine wouldn't turn at all. All the indicator lights and radio and headlights came on, but the starter wouldn't go. I checked the fuses visually and they all looked good. I couldn't check the relays in the fuse box, though. I put 3 500 watt flood lights under the car to heat it up and put some new antifreeze in it(I didn't flush it). That didn't help. Whenever I try to start it, the brake lights flash on and off like the hazards for about 30 seconds. I don't know what that means, but that may be a key. Please let me know if you have any good suggestions.