Don't turn over. Lights come on when key turned, then they go off, no cranking on 2005 Hyundai Tucson

The car used to not start without a jump if left idle for 24-48 hours. It would start after that. I took battery out charged it, put it back in. This time when turning the key the lights on dash come on but then they go out when it should be cranking. All lights stay out until I disconnect/reconnect the battery and try to start over. There was a new computer put in vehicle a short time ago but that didn't help the car to start up without a jump. Battery, alternator, starter good.

Asked by for the 2005 Hyundai Tucson
poss anti theft issue or starter
you are right it is a anti theft issue, but now the problem is it seems to have gone back after running a day or two with not turning over, like having to reset that antitheft thing again? The computer is a new one, and when plugging diagnostic in for codes it does not recognize the VIN # ? Could this cause all this to be happening. Battery still says full charge.
1 more answer
Sounds like a power issue. Make sure all wires and connections to the battery are tight and secure. if you have not yet done so, bring your battery to a parts store to get a proper reading and testing of your battery. Some bad batteries can still take charge but when put under load like a starter completely looses half of the voltage if not completely.