https://mega.nz/file/VUlGGJqJ#ReTF4oxCG1hPk3b4B-B7Lk1UWKSqhLxroXa_L1keA5c
Try this, including the exe version of the installation driver, and the inf driver (can manually right-click in the Windows system device manager to browse and install).
In addition, if the tablet can still be turned on, you can try to connect it to the computer in the power-on state, and then shut down or restart it to see if the port can be correctly recognized by spflashtool when the tablet is shut down or restarted.