Not much options to do anything wrong, I think.
But maybe not all packages that you need for knitting are installed yet (?)
I think you need at least the package
rmarkdown because installing that will also install packages as
knitr and other packages. Did you install that?
You can see which packages are installed by typing in the R console:
or checking the
packages panel you can also install
rmarkdown and dependencies (make sure that the
install dependencies field is flagged).
You did not tell on what type of system your are working and maybe it is not relevant in this case.
Bit if installing missing packages does not work, it could become relevant.
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