I have no idea what my Wi-Fi password is, so can't activate the Kindle. This is my 4th Kindle; I bought the others with no help, but have no record of Wi-fi password.

John,

Is it on a particular Wifi Connection?

Are you able to connect to other Wifi? Or other devices works fine on this particular Wifi Connection?

Go to Settings < Wi-Fi < Click/Tap on the Wi-Fi Network and Choose Forget

Enter the Password again and make new Connections.

It May help.

To connect to a Wi-Fi network with a hidden SSID, select Add Wi-Fi network from the settings. Then manually type in your SSID and password, and select your network security type. Select Save when finished. Now you can browse the web through your Wi-Fi router or connect to other network devices

trouble connecting my new Kindle to my wi-fi Mary, Check the attached links,instruction and guides to get kindle connected, Good luck
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
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Your kindle has a sim card installed for 3G (lifetime licence paid by amazon and paid for on purchase price on the unit) but that is not related to the wi-fi function on your kindle. Your wi-fi service needs to be logged in to with the same password as you use to log any computer on to your router when at home or whatever wi-fi password is required when elsewhere (e.g a bus, train or restaurant).

From the Home screen, press the Menu button.
Select Settings, and then select view next to Wi-Fi Settings.
In the list of detected networks, choose a network to connect to it.
If your Wi-Fi network and router support WPS (Wi-Fi Protected Setup), your Kindle will detect it.
If you don't see your network in the list, you need to add the network manually.
If the network is protected by a password or WPS (Wi-Fi Protected Setup), enter the password and then select Submit.If you don't know the Wi-Fi network password, contact the person who set up the Wi-Fi network.After you connect to a Wi-Fi network, your Kindle automatically connects to it again whenever that network is in range. If more than one network is in range, your Kindle automatically connects to the last network used.

Not positive but think you will have to unregister the Kindle and then re-register it. You will lose everything.

If the sky wi-fi is your own wi-fi service then the password is normally on a typed label stuck to the wi-fi router itself along with the SSID of the wi-fi network which should be the same as you have selected on the Kindle in confirmation you are connecting to the correct network.

If the sky wi-fi is not your own wi-fi then you will either need to contact the owner or administrator of that network or select a different wi-fi network to connect to as described in the Kindle Support web pages for your device.

From the owner of the Wi-Fi network.The password is usually set up in a network router to limit wireless access to authorized people.

If you have no idea what I am talking about, your Kindle probably located a neighbour's wireless internet access point and you cannot use it without his permission.