No power from battery

Car has been on a battery tender. It's less than 6 months old and has been starting the car fine. Trust me it's not the battery.

If you are positive that it is not the battery then it has to be the starter. Try tapping on starter with a hammer while trying to start vehicle at the same time if vehicle starts replace starter if no start most likely the starter solinoid.

I was initially thinking that but would either keep it from getting power to the rest of the electrical system such as lights, seats, ect?

If loose connection at starter solinoid could cause your problem.

I have cleaned and tightened all the connections but I'll look into it again. Thanks

I am going through the same issue on a 69’ Montego mx. So first off you are most likely right on it not being the starter. The cabin lights don’t pull power from the same side of the solenoid as the starter it pulls from the battery/alternator side. Second, you know the battery is good and the solenoid is new so that “should” be good lol next would be to check your voltage regulator. They are pretty cheap and are usually not hard to find in your vehicle. You can also take the voltage regulator to autozone and they can test it for you. If that is good check your ignition systems. So test your ignition switch and fuse box. If your are not getting power to your ignition switch then of course when you turn the key nothing will happen. You can test if your cables have a good connecting too by bridging the solenoid but be sure you know what you are doing before you attempt that. There are videos on how to do it on YouTube.