This question has been asked in: Configure proxy on Rstudio. However, it was never resolved.
I am a user of RStudio 0.99.486
version and R 3.2.2>
Thank you for your question. It helped me to resolve my issue. I had to unmark the option to use the settings from the Internet Explorer and restart.
Maybe your .Renviron does not contain the proxy port, you have to write
http_proxy=http://proxy.company_domain.es:8080/
http_proxy_user=user_name:password
If you specify
http_proxy_user=ask
it should prompt you for user name and password - then you know that the file is read