I see you’ve indicated your phone is a Moto 4. Is that a Moto E4, Moto G4 or Moto X4? If uncertain, please take a look here when signed into your Republic account and let us know: Phones | Republic Wireless.
given the app (linked by @SpeedingCheetah) there may be senor requiment that not published (Google Play is showing My Moto X2 and Moto Z2 Play are both compatible)
depending on your phone a budget (Moto E4) or mid-line (Moto G4) may be missing the accelerator and gyro sensors the app requires