I’m updating my Tstat8 to 9.4 firmware. Nine of ten thermostats upgraded correctly while one go stuck part way during the update. Now the thermostat is flashing (ON short, OFF short, ON short, OFF long ) and nothing is written on the screen while usually “Updating…” is printed) and doesn’t accept firmware upgrade anymore. I’ve tried also disconnecting it from T3 Controller and connecting it directly to USB RS485 key unsuccessfully: ISP tool reports “device is offline, please check the connection”. Connection is ok because I’ve tested several devices with diffenrt modbus ports.
Any idea to restore the thermostat in order to flash the firmware?