gnuplot latex documentation error with (MiKTeX 22.7)

[Tatsuro M. <tma...@ya...>]

I have a situation to make gnuplot.pdf on windows (MinGW-w64) with MiKTeX 22.7

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  :
  :
LaTeX Warning: Reference `set label' on page 70 undefined on input line 6036.


LaTeX Warning: Reference `hypertext' on page 70 undefined on input line 6059.



pdfTeX warning: pdflatex.exe (file ./figure_labels2.pdf): PDF inclusion: found
PDF version <1.7>, but at most version <1.5> allowed

! LaTeX Error: Unicode character ∙ (U+2219)
               not set up for use with LaTeX.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

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I have not met such error on MiKTeX 22.3.

Any suggestions are welcome.

Tatsuro