Error: pandoc document conversion failed with error 127 - knitr

Question

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output file: test.knit.md
/usr/lib/rstudio-server/bin/pandoc/pandoc +RTS -K512m -RTS test.utf8.md --to html --from markdown+autolink_bare_uris+ascii_identifiers+tex_math_single_backslash --output test.html --smart --email-obfuscation none --self-contained --standalone --section-divs --table-of-contents --toc-depth 3 --template /usr/lib64/R/library/rmarkdown/rmd/h/default.html --variable 'theme:cerulean' --include-in-header /tmp/Rtmp4CjD4R/rmarkdown-str6f6421e357bc.html --mathjax --variable 'mathjax-url:https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML' --highlight-style haddock
Error: pandoc document conversion failed with error 127
Occasionally, I run the codes and it completed 100% and created a md format file.
> traceback()
10: eval(expr, envir, enclos)
9: FUN(X[[i]], ...)
8: lapply(aesthetics, eval, envir = data, enclos = plot$plot_env)
7: f(..., self = self)
6: l$compute_aesthetics(d, plot)
5: f(l = layers[[i]], d = data[[i]])
4: by_layer(function(l, d) l$compute_aesthetics(d, plot))
3: ggplot_build(x)
2: print.ggplot(x)
1: function (x, ...)
UseMethod("print")(x)
There is no ggplot function run inside the RMarkdown but there is ggplot error when I tried to traceback(). However there is an error Error:127, any solution?
Googling the error message indicates that ‘status 127’ means that commands are not being found.