They are going to have the same problem they had with their original phones. No apps. They could never get enough developers to care about the OS without a user base. You also can’t get a user base without apps. That’s what killed the windows phone.
Amazon tried to use the kindle formula on a cell phone. The problem is that the main reason the kindle was successful was there was no real competition. They also only need to provide books not apps for the kindle. The cellphone market was a lot more mature with a ton of options. They came in with a mediocre phone that had less apps and less configurability. They tried to do the Apple walled garden on an Android phone. Clearly they didn’t understand their market.