Check the driver:
Make sure that the USB driver of Qualcomm 9008 mode is installed on your computer. You can try to reinstall or update the driver. You can usually download the latest driver from the official website of Qualcomm or the website of the mobile phone manufacturer.
Replace USB port or data cable:
Try connecting the phone with a different USB port, or replace the data cable. Sometimes, problems with ports or data lines can also lead to unstable connections.
Close other software that may occupy the COM port:
Make sure that no other software occupies the COM port. You can close other unnecessary software or disable other unnecessary ports through Device Manager.
Restart QPST software and mobile phone:
Close the QPST software, restart the computer and mobile phone, and then try to connect again.
Use different versions of QPST software:
Sometimes different versions of QPST software have different compatibility. Try using another version of QPST software.
Enter 9008 mode:
Make sure that the phone has entered Qualcomm 9008 mode correctly. Generally speaking, you can enter this mode through key combination or special software tools.
Check phone settings:
Some mobile phones may need to enable USB debugging mode in the developer options, so be sure to enable this option.