You need the latest update to connect to the internet again. However, the old kindles are quirky and had to be updated sequentially, so you'll have to update to 4.1.2 then 4.1.3 then 4.1.4. I went through this myself last week with a K4 I picked up at a secondhand shop to permanently keep in my bag.
Here is the support article with the link to each:
https://www.amazon.com/gp/help/custo...DD8E64F7AAEF8A
Also, if you have 2FA enabled, add the code to the end of your password when you try to log in. No need to disable it.