Knitr not working on markdown not able to generate html


Please ask your questions about R Markdown here.
knitr not able produce html
it is flashing error message as follows.
Error in get(Info[i, 1], envir = env) :
cannot open file 'C:/Users/acer/Documents/R/win-library/3.5/rprojroot/R/rprojroot.rdb': No such file or directory
Calls: :: ... tryCatch -> tryCatchList -> tryCatchOne ->
Execution halted.
Anybody have any suggestion /solution.
R version:3.5 Studio version1.1.456