Open the driver's Advanced Properties page. Verify that hardware flow control (RTS/CTS) is actively enabled if your cable supports it. Ensure the 128-byte FIFO is maximized to give the OS more time to process incoming data packets. Issue: Missing COM Ports after Windows Update
Once installed, you should manually verify that the driver is utilizing the hardware’s full potential: 16c95x serial port driver
if you need extreme low power or very simple 9600 bps-only systems (a basic 16550A suffices). Open the driver's Advanced Properties page
What is the of your serial expansion card? Issue: Missing COM Ports after Windows Update Once
This usually occurs when there is a resource conflict (IRQ or I/O memory addresses) between the PCIe serial card and another component on your motherboard, or if the driver is fundamentally incompatible with your version of Windows (e.g., trying to run an old 32-bit Windows 7 driver on a 64-bit Windows 11 system).