Rstudio will not launch: "This site can't be reached 127.0.0.1 refused to connect"

See also:

This issue should be fixed in the latest release of RStudio, but evidently it is not in your case. Can you try the following:

export DYLD_INSERT_LIBRARIES=/Library/Frameworks/R.framework/Resources/lib/libR.dylib
/Applications/RStudio.app/Contents/MacOS/RStudio

and see if you have any better luck?

I'm also curious whether having anaconda3 on the PATH is causing issues for you. What is the output of:

which R

on your system?