I have a similar problem to the above. RStudio does not start all of a sudden. Below is my diagnostics report;
/Applications/RStudio.app/Contents/MacOS/RStudio --run-diagnostics
27 Feb 2019 12:40:14 [rdesktop] ERROR system error 100 (Protocol error) [description=Unable to parse version from R, version-info=, r-error=dyld: Library not loaded: /usr/local/opt/readline/lib/libreadline.7.dylib
Referenced from: /usr/local/Cellar/r/3.5.1/lib/libR.dylib
Reason: image not found
]; OCCURRED AT: rstudio::core::Error rstudio::core::r_util::rVersion(const rstudio::core::FilePath &, const rstudio::core::FilePath &, const std::string &, std::string *) /Users/rstudio/rstudio/src/cpp/core/r_util/REnvironmentPosix.cpp:784; LOGGED FROM: bool rstudio::core::r_util::detectREnvironment(const rstudio::core::FilePath &, const rstudio::core::FilePath &, const std::string &, std::string *, std::string *, EnvironmentVars *, std::string *) /Users/rstudio/rstudio/src/cpp/core/r_util/REnvironmentPosix.cpp:678
Using R script: /usr/local/Cellar/r/3.5.1/bin/R
Attempting to launch R session...
R_HOME=/usr/local/Cellar/r/3.5.1/lib/R
R_DOC_DIR=/usr/local/Cellar/r/3.5.1/lib/R/doc
R_INCLUDE_DIR=/usr/local/Cellar/r/3.5.1/lib/R/include
R_SHARE_DIR=/usr/local/Cellar/r/3.5.1/lib/R/share
LD_LIBRARY_PATH=/Users/kwesi/ferret/pyferret-7.4-MacOSX-Python-2.7/lib/python2.7/site-packages/pyferret
PATH=/usr/local/opt/coreutils/libexec/gnubin:/Users/kwesi/ferret/pyferret-7.4-MacOSX-Python-2.7/bin:/Users/kwesi/bin:/usr/local/bin:/Users/kwesi/anaconda2/bin:/opt/local/bin:/opt/local/sbin:/Users/kwesi/ferret/ferret-7.4.2-MacOSX/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin
HOME=/Users/kwesi
27 Feb 2019 12:40:24 [rdesktop] ERROR system error 60 (Operation timed out); OCCURRED AT: rstudio::core::Error rstudio::core::waitWithTimeout(const boost::function<WaitResult ()> &, int, int, int) /Users/rstudio/rstudio/src/cpp/core/WaitUtils.cpp:63; LOGGED FROM: -[AppDelegate applicationDidFinishLaunching:] /Users/rstudio/rstudio/src/cpp/desktop-mac/AppDelegate.mm:365
Any help is much appreciated. Thanks