Windows 10 strictly blocks drivers that lack a modern digital signature. Since the U232 P9 driver is legacy software, you may need to temporarily bypass this restriction:
Windows 10 "Windows Update" may try to overwrite your working driver with the non-functional newer version during the next update cycle. u232 p9 driver windows 10
If you are seeing a yellow warning icon next to the USB Serial Port in Device Manager, the issue is almost certainly the driver version. Step-by-Step: Installing U232 P9 Driver on Windows 10 Windows 10 strictly blocks drivers that lack a