If the ETC shut down without oxygen, it could be due to a variety of reasons. One possibility is that the fuel cells are not receiving enough oxygen to generate power. Another possibility is that the system is overheating and needs to be shut down in order to prevent damage.
It is also possible that there is a problem with the oxygen delivery system itself, which could be caused by a leak or blockage. If the ETC does shut down due to lack of oxygen, it is important to identify the cause so that it can be fixed. Otherwise, the ETC may not be able to restart and function properly.