Hi, I'm Nathan.Sorry to hear that you're having trouble with this but I'll do my best to help you.
Which model kindle do you have?
Have you ever updated its software?
Thanks for confirming.
3g connectivity has actually been discontinued in most areas, however even if it is in service for your area and model, it will not function until the kindle software is updated, which is a manual process.
Can you go into the kindle menu under settings, then About/device (you may need to go to the home menu first, then to settings button again) and tell me what you see as the current Software Version on the kindle?
Yes that is what I needed, thank you,
That version is actually quite out of date,
back in march amazon sent out alerts to all kindle users that their devices needed a new form of update to stay compatible, and it appears yours was not updated back then, and has now lost compatibility at this point.
So you will have to manually update it now to make it work again.
to download the latest version,
you'll need to plug the kindle into your computer via the usb cable, then manually drag/drop or copy/paste the update file into the kindle "drive" on your computer.
This should restore functionality for you.
Do you need more help with this?