I replace the batteries in the round remote start button and cannot get if to work now also the other key fob with ignition key the buttons don't work please help

Hi Samantha.

First thing to check is that the batteries are correct size and inserted in correct direction.

Next is that the contacts are clean and there are no protective stickers over the battery.

After that it is worth getting some fresh batteries and trying with those as there are often fake / faulty batteries sold on the internet, so try getting some from a reputable source.

If still no joy come back to us.

This may help: https://www.youtube.com/watch?v=YfmuD40Vvj8

It is also possible they just need reattaching to the car so this video might help: https://www.youtube.com/watch?v=MYhtrHHYLF0
Good Luck

John