Setup Fire TV Stick (3rd Generation)

Many cause behind that for Alexa Not connecting to Fire TV
Loose connection for Alexa Setup device and Fire TV
Wi-Fi connectivity issues between Alexa and router and smart phone
Alexa is may be the switch mode
Alexa App not updated
Alexa firmware not updated may also arise the problem during connectivity with smart home device
Lastly: you need to fix the above problem or contact the Alexa expert and get the solution for Alexa Won't connect to Fire TV.

Basic Troubleshooting for Amazon Fire TV Try these common solutions to resolve issues like a blank screen, app errors, and problems with your display or audio.
Can't Connect to Wi-Fi for common solutions that may help.
Amazon Fire TV is Frozen, Blank, or Won't Power On for solutions.
Change Your 1-Click Settings. Manage Your Apps & Games.Contacting Your TV Manufacturer .
About 4K Ultra HD on Amazon Fire TV (2nd or 3rd Generation)Check the Video Resolution section under Display to make sure your connected TV meets HDCP 2.2 system requirements for watching video in 4K Ultra HD. For more information, go to Watching Video in 4K Ultra HD on Fire TV.

Calibrate Your Display

If part of your display is missing or cut off at the edges of your screen, your TV may be automatically scaling your picture.
You can use the Calibrate Display tool (Settings > Display & Sounds > Display > Calibrate Display) to adjust for this.
When you open the tool, you'll see four grey arrows pointing to the edges of your screen, which you can use as a guide when making your adjustments. Press the Up and Down keys on your Fire TV remote until the grey arrows are completely visible and touching the edges of your screen.
Contacting Your TV Manufacturer .Follow the on-screen instructions to make adjustments with your TV remote. You should still see the grey arrows from the Calibrate Display tool--make sure the tips of the arrows are completely visible and touching the edges of your screen.
Amazon Video Settings and Devices on the Amazon website.
Go to the Parental Controls section and enter a new 5-digit PIN under Amazon Video PIN. Then select Reset Your PIN.
MicroSD Storage for Amazon Fire TV (2nd Generation) .
USB Storage for Amazon Fire TV (1st Generation).If your storage device is compatible, try safely removing and then re-attaching it to your Amazon Fire TV:

1. Select Settings > Device from the Fire TV menu, and then select your storage device.
2. Select Eject.
3. Wait for the on-screen confirmation before safely removing the device.
4. Re-attach your storage device.

Please go to your setup page on your menu. There should be instructions, step by step, to help you throughout the entire process. I have copied the below from the Amazon website:

Register or Deregister Your Fire TV Register your device to make sure you have access to the latest software, features, and functionality that power Fire TV.

Registration connects your device to your Amazon account so you can access and manage your content. It also makes sure your device has access to the latest software and features available for Fire TV.

As part of first-time setup, you'll see on-screen instructions on how to register your device by entering your Amazon account information. You may also be prompted to enter a code on the Amazon website as an added verification step.
Tip: If you purchased your device from the Amazon website, it should be automatically registered to the Amazon account you used to place your order. When your device arrives, you can verify that it's registered to you by selecting Settings > My Account from the Fire TV menu.
You can also view or change the account your device is registered to from Settings:

1. Select Settings from the Fire TV menu.
2. Go to My Account.
   • If your device isn't registered, a Register option displays on this screen. Select Register and enter your Amazon account information when prompted.
   • If your device is currently registered, the name associated with your account displays in this section. If you select it, you'll then see a Deregister option you can use to connect your Fire TV to a different Amazon account. After you deregister, you'll be prompted to register again by entering your preferred Amazon account information.

Note: When you deregister, all of your Amazon content is removed from your device, and many Fire TV features will no longer work.

Register or Deregister Your Amazon Fire TV - Amazon.com

https://www.amazon.com/gp/help/.../display.html?...

Amazon.com, Inc.New Year New You. All .... Register or Deregister Your Amazon Fire TV Device ... If you purchased your Amazon Fire TV device from another retailer or received it as agift, follow the on-screen ... From the Home screen, select Settings > My Account. ...Differences between Amazon Fire TV and Fire TV Stick · Amazon Fire TV ...

How to Get Your New Fire TV Device Up and Running - Wired

www.wired.com/2014/12/amazon-fire-tv-setup/

WiredDec 25, 2014 - Here's how to take that new Fire TV device from zero to streaming in five ... If you received an Amazon Fire TV box or stick in your gift haul, .... Got an amazon fire tv stick and cannot access the home screen to register with my ...