Hello john.yang@gentherm.com,
This seems to be a problem with the selected drive for the download. What version of the toolbox are you using? If you have the 3.0, I'd advise you to get the new 2018.R1 version as it has some new blocks and some bugs fixed. If you have some specific reason for why you want to continue using the 3.0 version, to fix this problem you'll need to go to settings (double click on the configuration block or press CTRL+E), go to download tab from code generation and there put the drive letter on which the S32K was mounted. You can check it out in My Computer, it should have a distinct name (something like S32K144EVB). If it is mounted on D disk for example, just write D in that option. If you have the latest release (2018R1), just double click the configuration block and go to download options, there you can click under the OpenSDA tab on the Refresh button, then chose from the list on the left the coresponding option; but note that in this list there will be all COM ports that are used at that point in time, so if it's more than 1, you'll still have to check which one is the board you're looking to connect to.
Hope this helps,
Razvan.