Hi Hyeonbin,
the 'flexgui-app-spm.bat' is the correct file. I have downloaded the "FlexGUI for PF8100/8200/8101/8201/8121 family (REV 1.01) and I also couldn't lunch the GUI.
I needed to download and install a Java Runtime Environment. Please download it from this link. If you already have the Java Runtime Environment, please uninstall it and install it again. Also please make sure, you have English language selected in your computer.
https://support.microsoft.com/en-us/windows/manage-display-language-settings-in-windows-10-219f28b0-...
After these installation and setting completed, please double click on the 'flexgui-app-spm.bat'.
JozefKozon_0-1613465916128.png
And a FluxGUI launcher should open.
JozefKozon_1-1613465968568.png
I hope it will help.
With Best Regards,
Jozef