Rmarkdown seams not working as usual after installing R3.4.3:
When knitting that HTML-Template:
--- title: \"Untitled\" output: html_document ---
Adding "self_contained: no" should remove the error message.
--- title: "R Notebook" output: html_document: self_contained: no ---
Source: Error when knitting default RMarkdown file in RStudio - @UsamaFoad