First, check and see if one of the outlets is plugged. If not, have a plumber re-plumb the valve correctly. Second, make sure the hot and cold inlets were piped correctly and that the valve was not installed upside down which would reverse the hot and cold inlets. The plumber may have to re-plumb the valve correctly. Reset check stops and clean the filter on the cartridge per instructions.
What do I do when I'm only getting all hot or all cold water out of my thermostatic valve?
Make sure the hot and cold inlets were piped correctly and that the valve was not installed upside down which would reverse the hot and cold inlets. The plumber may have to re-plumb the valve correctly.
Why isn't the water reaching as hot as 120° on my thermostatic valve?
Make sure the hot water source has the temperature set high enough, it should be at least 140 degrees for the thermostatic valve to reach its 120 degree max. If the stem of the thermostatic cartridge was turned prior to install, the cartridge could be out of calibration, refer to the installation instructions on how to recalibrate the cartridge. Clean out the cartridge and check stops for any debris, refer to the installation instructions.