I have the same issue. Can't pair replacement remote. Toshiba43LF621U19 fire TV. I have to go into my app on android phone to be able to work the TV. Replacement remote is alexa voice remote. I thought it was same as I had originally but won't pair. I have unplugged tv, held down home button 20 different times or more. Is this not right remote? TV has been a pain from the start and this just adds to the frustration.
Welcome! Did you buy remote A or remote B? Remote A is for Fire TV devices (but not Fire TV Edition TV), whereas remote B is specifically for Toshiba and Insignia Fire TV Edition TVs.