If you have a newer device that won't let you bypass the update but you have it blocked via your router.. you can use the Fire TV app for your phone search for the fire device connect and then from there it lets you register your device and bypass the update...
Didn't work for me. I pulled the power on my router just as it connected and before it said checking for updates and then again after it connected but just as it started saying checking for updates. Both times I re-entered the wifi login info. Even though the internet was gone it just said "unable to update your fire stick". This thing is currently an unsuable stick at the moment