Device is recognized but not answer

[iDoka]

I tried CANtact on WinXP and RHEL OS.
Both system recognize device but dont communicate by serial.
In WinXP I used CANHacker SW, in RHEL I used GTKterm (run as root).
CANHacker reported: CAN interface not responding.
In GTKterm I didnt receive response for any command ( V for example).
Is it depends on the COM-port speed? I tried 38400, 57600, 115200 - unsuccessful.

RHEL diagnostic:

$ tail /var/log/messages
Nov 23 00:02:36 localhost kernel: usb 3-4.4: new full-speed USB device number 38 using xhci_hcd
Nov 23 00:02:36 localhost kernel: usb 3-4.4: New USB device found, idVendor=ad50, idProduct=60c4
Nov 23 00:02:36 localhost kernel: usb 3-4.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Nov 23 00:02:36 localhost kernel: usb 3-4.4: Product: CANtact dev
Nov 23 00:02:36 localhost kernel: usb 3-4.4: Manufacturer: CANtact
Nov 23 00:02:36 localhost kernel: usb 3-4.4: SerialNumber: 00000000001A
Nov 23 00:02:36 localhost kernel: cdc_acm 3-4.4:1.0: ttyACM0: USB ACM device

PS: one thing different: I used STM32F072RBT6 chip instead F042C6T6 (also change LD-script and assembler startup file from latest CMSIS).

What approach I should use for my issue diagnostic?

[iDoka]

I tryed build the original version from github for STM32F042C6,
after flashing I saw the same symptoms - no answer by COM-port from/to host.

Perhaps the issue in GNU toolchain. Could you provide which version of gcc did you use?