2008 430sc Lexus how do we get keyless entry and seats to work after

Whoops that sounds like the BCM lost the programming. This happens when main power is disconnected without using the memory saver tools. So now you will need to find a shop that can do a re-flash. If you can’t find one then your stuck with the dealership.

Could still be the battery, Put a volt meter across the terminals and see if you have about 14 volts. Less than that might be too low to crank the engine or fully power up the ECM.

14 volts when test with a multi meter? Maybe with the motor running and doing an alternator test. the lights will always be on when a battery is connected to the cables, and the light switch is on. It's something interior if it doesn't start. Maybe the battery wont start under "load." I tested an Interstate battery for 3 weeks and it always held a 12.4 to 12.6 charge, without being connected. 14 is a little high to me, jmo.

You stick with your "at rest" battery voltage and I'll stick with mine and, yes, any style of volt meter will work just fine.