I tried downgrade procedure according to the instructions for TFTP software.
I used IPC_G3_EN_STD_5.5.131_210120.zip
After starting tftpserv.exe I only have :
2022-11-25 20:32:29] TFTP server [192.0.0.128] initialized
TFTP server didn't find the camera. Not jump to the testing device step :(...