If pcmtuner pcmflash application says unable to use selected interface j2534 scanmatic SM2 USB (shown image below), it can be a driver issue.
If you have installed the driver, delete it and reinstall driver.
If don’t install scanmatik driver, download pcmtuner scanmatic driver here
If had this error during pcmtuner software installation,
If update pcmflash to 1.2.5 by mistake, delete pcmflash 1.2.5 and reinstall pcmflash 1.2.0.
Download pcmflash 1.2.0 here