Unable to run devtool, dplyr, gitthub, Rtools in R 4.0.2

[AAA000]

I am working on a Probability and R Specialization course online, and the recommended version for R is 4.0.2. I installed it step by step, and began working on the project assigned. But devtools, the first package to be installed is not available for R Version 4.0.2.
I have installed RTools40 from CRAN but have been unable to run it in RStudio because it can't access it.
I tried creating a Renviron file but have been unable to run that too.
I am all out of options, and I have to move on in the course. Any help at all would be massively appreciated.

[technocrat]

This comes up often among Win users. As shown in the linked posts, a variety of problems can occur.

While troubleshooting this, create a free RStudio Cloud account to be able to start your coursework.

After looking over the linked posts come back with any additional information about your setup that appears related.

[andresrcs]

Can you post the complete message you get when you try to install devtools?

[AAA000]

Hi

Thank you for responding to my query.
So I enter the command- install.packages("devtools")
And this is what I get -

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'
Installing package into ‘C:/Users/Sharma JI/Documents/R/win-library/4.0’
(as ‘lib’ is unspecified)

Adding the remaining command in the next message

I'm sending the response just for devtools, but I get the same message for other packages too-whether it's github, or dplyr or shiny.
I had, for the first time run RStudio through D:/ in my laptop, and the packages had installed then. After some commands weren't running as mentioned and I realized my error I uninstalled and reinstalled it via C:/ drive. It is now that none of the packages are loading.

[AAA000]

2. 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'

[AAA000]

3. Warning in install.packages :
   package ‘devtools’ is not available (for R version 4.0.2)
   Warning in install.packages :
   unable to access index for repository https://cran.rstudio.com/bin/windows/contrib/4.0:
   cannot open URL 'https://cran.rstudio.com/bin/windows/contrib/4.0/PACKAGES'

[AAA000]

Also none of these packages are available in the packages index in the Files, either to install or update.

[andresrcs]

This seems like a connectivity issue, R is not being able to connect to the CRAN repository you have selected, these are some things to try.

• Choose a different CRAN repository, RStudios repository is a good choice (http://cran.rstudio.com/) or you could choose one that is geographically closer to you.
  
  
• Disable secure download setting.
  
  
• Check if your internet connection has traffic restrictions of some kind, like a firewall, proxy server, etc. This is usually the case when you are at work or school.