After Save Only generate a 0kb tmp fire

I spent a few days building a model on Sketchup, and finally
clicked to save. Automatic saving every 5 minutes is turned on, but
only a Okb tmp file appears. Changing its suffix prompts “This is
not a sketchup file”. After opening the original file, it is still the
beginning, and no skb file has been generated. How can I retrieve
my progress?