I've seen a few threads on RStudio terminal issues (e.g Cannot use terminal: no window contents - #4 by Aurele) but was not able to resolve on my system by toggling "connect with websockets" or changing between CMD Prompt, PowerShell, etc. The other options like "Local Terminal Echo" and "Save and restore environment variables" do not appear to be available in my RStudio version.
My terminal diagnostics and sessionInfo() are below. I'm running RStudio version 1.1.456.
I can open git bash from the "Tools/Shell/" menu item.
Global Terminal Information --------------------------- Loaded TerminalSessions: 0 Terminal List Count: 3 Handle: '10C5D73' Caption: 'Terminal 1' Session Created: true Handle: 'A28521A1' Caption: 'Terminal 2' Session Created: true Handle: '3AD10975' Caption: 'Terminal 3' Session Created: true
R version 3.6.1 (2019-07-05) Platform: x86_64-w64-mingw32/x64 (64-bit) Running under: Windows >= 8 x64 (build 9200) Matrix products: default locale:  LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252  LC_MONETARY=English_United States.1252 LC_NUMERIC=C  LC_TIME=English_United States.1252 attached base packages:  stats graphics grDevices utils datasets methods base loaded via a namespace (and not attached):  compiler_3.6.1 rsconnect_0.8.13 tools_3.6.1 rstudioapi_0.10 yaml_2.2.0