Modbus USB Dongle remote diagnostics

Are you sure you dont have any other program connected to that com port? As only one "master" can be connected.

Some steps how to fix it:

Check Device Manager for Port Usage

• Open Device Manager (devmgmt.msc) and expand the Ports (COM & LPT) section.
• If you see multiple COM ports marked as "in use" (but you know they are disconnected), this can happen because Windows does not automatically remove unused or ghost devices.
• To fix this:
  • Go to View > Show Hidden Devices in Device Manager.
  • Look for any gray (disconnected) COM ports.
  • Right-click on these and choose Uninstall Device to remove them manually.
  • Uninstall and reinstall the driver for the Modbus USB dongle. Ensure you're using the latest version provided by the manufacturer
  • Disconnect the USB dongle, restart the server, and then reconnect it to see if it reassociates with a new or available COM port.

You can't do this from bOS config though.

Unrelated but I just had a dead chinesium usb ch340 dongle, it worked fine for about 4 years. Now it only shows communication error. Voltages were all fine. Luckily I had a spare and it worked so the connected devices were all fine. So yeah they will not work forever and may die randomly...

I'll swap dongles but I have to go to installation site :( That's why I was asking about remote diagnostics.. I asked customer to place it (dongle) in another usb port, I've changed COM in BoS Config but still no luck :( The same error so I assume dongle died..

Ok, thanks. No, it worked for a year or something. No changes within this period. I'd do that but it assumes I have admin password for Windows IoT of Grinder server.. and I assume CC won't give me that password ;)