nbconvert failed: PDF creating failed, captured latex output:
This is XeTeX, Version 3.14159265-2.6-0.99999 (TeX Live 2018/W32TeX) (preloaded format=xelatex)
restricted \write18 enabled.
entering extended mode
! Undefined control sequence.
< > .\notebook
.tex
?
! Emergency stop.
< > .\notebook
.tex
No pages of output.
Transcript written on ?.

solution:
1, if the file path with Chinese, remove the Chinese
2, find the installation path under the PDF. Py file open
… \site-packages\nbconvert\exporters\pdf.py

#writer = Instance("nbconvert.writers.FilesWriter", args=(), kw={'build_directory': '.'})
writer = Instance("nbconvert.writers.FilesWriter", args=(), kw={'build_directory': ''})

The

and 'build_directory' : '. ' to ' build_directory ':'