Are you using this one:
If so did you get all 3 files?
- Parent app RAW link... https://raw.githubusercontent.com/NelsonClark/Hubitat/main/Apps/Advanced_vThermostat/Advanced_vThermostat-Parent.groovy
- Child app RAW link... https://raw.githubusercontent.com/NelsonClark/Hubitat/main/Apps/Advanced_vThermostat/Advanced_vThermostat-Child.groovy
- Device RAW link... https://raw.githubusercontent.com/NelsonClark/Hubitat/main/Apps/Advanced_vThermostat/Advanced_vThermostat-Device.groovy