I am using RStudio 1.2.1335 on macOs Mojanve 10.14.5.
R version 3.6.1 (2019-07-05)
I cannot open either a .R file or a .Rmd file using the File>Open File menu. I have tried creating a new .R file and opening it but it does not open. Using the menu I can import a file.
This happened after I did a number of updates to RStudio, R, and the operating system.
I notice that I can't open R directly at this point either--has to go through R Studio. Generally not a problem but I was going to check if I could open a file in base R.
To get at these files I have to open them in a text editor and copy and paste to an R studio window. I have tried also clicking on them using Finder and explicitly opening with R studio.
I would guess you lost/damaged your R installation (which is distinct from RStudio). If possible I would try reinstalling just the R portion from https://cran.r-project.org . At the least that might give you a diagnostic during the attempt.
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