You should have Rc, G, W1 wiring instead.
For a heat-only system, you should have the connections R, G, and W1. The G wire can be repurposed as a C-wire.
- Identify the G wire at your control board.
- Connect the G wire to the C terminal at the control board.
- At the thermostat, label the G wire from the old thermostat as C-wire.
- Follow the Wyze app to continue the installation process, selecting Rc, C, W.
Note: To keep fan control, you will need to add an additional jumper wire between the G terminal and the W terminal.