PU letter and work visa

Good day! I am Ukrainian, currently in Ukraine. My work and residence permit expired a month ago. According to a new regulation released on 23, September, I am able to apply for a new visa without a PU letter in order to come back to a previous employer. But I found a new employer in China, do I still need a PU letter or a normal invitation letter is enough? I can't reach Chinese embassy in Ukraine, could you please tell me what is the best way to reach them? Thank you a lot!