"Key not detected" - Is the keyfob battery just low?

[NavinRJohnson]

Does anyone know? My FFE is four years old, so it seems fitting the battery might just be low, but it's doing this now with increasing frequency. Anyone by chance know how to open/replace the battery? I did notice there's a small switch/lever on the back but it doesn't seem to do anything. Suggestions?

 

[Pearl]

https://www.youtube.com/watch?v=cc5_vTTPZV8