Hello! My name is Ben a fellow member here in the community, not a Microsoft employee. Hope you are doing well!
As for the issue where your fire tv is not being detected, it could be on how you are configuring your TV and not really your Windows 11 PC.
- You must enable mirroring mode to stream from a PC to an Amazon Fire TV stick. You can do this by pressing and holding the Home button until a menu appears on your Fire TV remote.
- Select Mirroring, and leave this page open. Then go to your computer and hit the Windows + K combo, if using Windows 11. The option is also in the menu available when you click on the Wi-Fi, Sound, and Battery section in the bottom-right corner. If not, click on the Pencil icon, select Add, and pick Cast.
Find and select your Fire TV device.
Hit Connect.
I hope the information above helps. Feel free to post back if you need more help and we fellow members are here to share our knowledge and assist.
Kind regards,
Ben