The problem with the Tuya/SmartLife integration is that many devices are not compatible with the integration.
Go into the Tuya/SmartLife App open the device, on the detail page in the upper right corner there is a pencil or 3 dots. Click on that and the new page should show a 3rd party control section. Things like Alexa and Google will be shown. If Smartthings is shown it should work, but ST is not show that means there is no Smartthings Integration.
If Smartthings is NOT listed there is work around that will give you a partial one way integration.
Another thing is that the Tuya integration seems to work better that the SmartLife integration. You can keep the devices in the SmartLife App and use the Tuya integration.