m172 plc unable to start communication

[PrecisionSummers]

Unable to connect to the M172 PLC via the usb. We had connections one day and then the next day received the "Unable to Start communications, Choose "on-line / Setup Communications" to configure it. The configuration has not changed. The PC has been restarted and the PLC has been restarted but sill not able to communicate. 

[StevenCho]

Unless hardware issue and incorrect COM port, the connection error occurred sometimes.

When It happen, I do mouse left-click on program section and try again.

But if it is not working, maybe hardware problem. 
Few days ago, I had hardware issue so I sent to Schneider Service team.

By the way, did you tried Connection through TCP?

[PrecisionSummers]

I tried TCP but sill no luck. 

[Bastian_Schmitz]

USB should normaly work. To test that the cable is proper recognized you can check the com port in the software. If you choose the correct com port Baudrate should be not longer selectable. Because over USB you could use every Baudrate.