'rstudio knit still turn rmd file

In RStudio, I used to be able to knit into whatever format, HTML, PDF, Word, etc. However today my rmd file I am trying to knit to HTML, PDF, or Word, and the Rstudio just spit out the same rmd file, with a dash ("-") in between space of the name. I tried for all rmd file and it's the same thing, i.e. not a knitted file but the same rmd file with the dash. What should I do?



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