Some Tuya devices do not use only MQTT, it uses also some (for now unknown - not reverse-engineered) protocols to send data.
see here https://github.com/codetheweb/tuyapi/discussions/502
Try using smartLife to do commands and see the MQTT exchange in node-red: this helps you to identify the DPs. (see a guide here).
If really you don't found an MQTT command, the only solution I found to control ALL Tuya devices is to trigger via node-red some ad-hoc Tuya 'automation'.
To do this (and more IOT functions) I developed TuyaDAEMON, an IOT framework.
An basic trigger implementation can be found here.
Now I'm working on solar extensions (see TuyaDAEMON e il fotovoltaico).
Hope that this gives you some help.
