Can't connect to CRAN mirror from RStudio - r

Question

This is my first post in the stack though this has been my go to option for any coding related issue for a long time. So recently my machine was reconfigured and I had to reinstall with the IT support all my IDEs including R and RStudio. Since then I am getting this vexing issue of installing any new R package and even existing R packages keep throwing error that it's not installed or can't connect to CRAN mirror
> .libPaths()
[1] "H:/My Documents/R/R-3.3.2" "H:/My Documents/R/R-3.3.2/library" "C:/R/R-3.5.3/library"
> .libPaths("C:/R/R-3.5.3/library")
> install.packages("DBI",repos="https://cran.rstudio.com/")
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
unable to access index for repository http://cran.rstudio.com/src/contrib:
cannot open URL 'http://cran.rstudio.com/src/contrib/PACKAGES'
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
unable to access index for repository https://cran.rstudio.com/src/contrib:
cannot open URL 'https://cran.rstudio.com/src/contrib/PACKAGES'
Warning in install.packages :
package ‘DBI’ is not available (for R version 3.5.3)
Warning in install.packages :
InternetOpenUrl failed: 'The server name or address could not be resolved'
Warning in install.packages :
I saw this was posted in another thread here:
R - cannot access urls for package installation
I tried all recommendations in here, still couldn't get it fixed. Any idea what else could be broken. Much appreciate your reponse. BTW, I am not an R pro either, just a little bit hands on.