This is often caused by doing Windows updates, which re-writes some of your Windows settings or causes issues with the USB driver.

More often than not, you may have USB power management enabled, which puts your USB port into "sleep mode" after set period of time (usually 15 or 20 minutes).

Please check these things:

A. USB port connection is working

1. Connect the HPLC to your computer via USB.

2. Turn on the HPLC instrument.

3. Go to Windows Settings->Bluetooth & devices->View more devices

4. You should see the HPLC connected to your USB and using the installed USB driver (Silicon Labs or FTDI).

Note: If your HPLC instrument is not powered ON, you will not see it connected to your computer. If you do not see the USB connection, then you may need to reinstall the USB driver or switch the cable to using RS232 to USB connection. Please contact us for guidance.

B. Check the USB power management settings

1. Go to Windows Settings->Bluetooth & Devices->scroll down to see "USB".

2. Change the USB battery saver to OFF.

3. Windows 10/older Windows versions have this setting in Control Panel->Power Options

4. Choose whichever Power management you are using and click "Change plan settings".

5. Then click "Change advanced power settings".

6. You should see "USB" setting here, where you can modify/disable USB sleep mode.