I have active internet LAN connection on my desktop, while installing packages 'plyr', 'dplyr' and 'ggplot2' error message displayed. Please help me. Error message is like:

<pre class="GNKRCKGCGSB" id="rstudio_console_output" style="font-family: 'Lucida Console'; font-size: 10pt !important; outline: none; border: none; word-break: break-all; margin: 0px; -webkit-user-select: text; white-space: pre-wrap !important; line-height: 15px; color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: -webkit-left; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" tabindex="0"><span><span class="GNKRCKGCMSB ace_keyword" style="color: blue; white-space: pre; -webkit-user-select: text;">> </span><span class="GNKRCKGCMRB ace_keyword" style="color: blue;">install.packages("ggplot2") </span><span class="GNKRCKGCGSB" style="outline: none; border: none; word-break: break-all; margin: 0px; -webkit-user-select: text; white-space: pre-wrap !important;">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' </span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);">Installing package into ‘C:/Users/admin/Documents/R/win-library/3.6’ (as ‘lib’ is unspecified) </span><span class="GNKRCKGCGSB" style="outline: none; border: none; word-break: break-all; margin: 0px; -webkit-user-select: text; white-space: pre-wrap !important;">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 : package ‘ggplot2’ is not available (for R version 3.6.1) Warning in install.packages : unable to access index for repository http://cran.rstudio.com/bin/windows/contrib/3.6: cannot open URL 'http://cran.rstudio.com/bin/windows/contrib/3.6/PACKAGES' </span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);">Warning message: </span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);">In download.file(mirrors_csv_url, destfile = mirrors_csv, quiet = TRUE) : </span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);"> </span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);"> InternetOpenUrl failed: 'A connection with the server could not be established'

</span></span>Thank you.
<span><span class="GNKRCKGCASB ace_constant" style="color: rgb(197, 6, 11);"></span></span></pre>