Sublime text keyboard shortcut binding not functioning

Following the instructions here, I've set up a new installation of SublimeText for use with R. I have no other SublimeText plug-ins installed. The keyboard shortcuts that are setup using the instructions in the link above don't work. I've set up my user key binding file as specified in the tutorial.

There are no conflicting key bindings in the 'Default' key bindings file.

Nonetheless, I can execute my R code in REPL by clicking through the menus:

Tools > SublimeREPL > Eval in REPL > Selection (Ctrl+Shift+R)

If I actually press the Ctrl+Shift+R shortcut, nothing happens.

Here's a copy of my user key binding file:

[
// Modified Sublime-REPL keybindings for an "R-friendly" set of shortcuts.
// For more information, see http://tomschenkjr.net/2012/05/17/using-sublime-text-2-for-r/

// Executes a selection of text in REPL, latter only displays code and does not execute
{ "keys": ["ctrl+shift+r"], "command": "repl_transfer_current", "args": {"scope": "selection"}},
{ "keys": ["ctrl+shift+r", "r"], "command": "repl_transfer_current", "args": {"scope": "selection", "action":"view_write"}},

// Executes the entire file (build) in REPL, latter only displays code and does not execute
{ "keys": ["ctrl + f7"], "command": "repl_transfer_current", "args": {"scope": "file"}},
{ "keys": ["ctrl + f7", "r"], "command": "repl_transfer_current", "args": {"scope": "file", "action":"view_write"}},

// Executes line(s) of text in REPL terminal, latter only displays code and does not execute
{ "keys": ["ctrl+alt+r"], "command": "repl_transfer_current", "args": {"scope": "lines"}},
{ "keys": ["ctrl+alt+r", "r"], "command": "repl_transfer_current", "args": {"scope": "lines", "action":"view_write"}},

// Executes a block (e.g., a custom function) of text in REPL terminal, latter only displays code and does not execute
{ "keys": ["ctrl+shift+alt+r"], "command": "repl_transfer_current", "args": {"scope": "block"}},
{ "keys": ["ctrl+shift+alt+r", "r"], "command": "repl_transfer_current", "args": {"scope": "block", "action":"view_write"}}

]

What am I doing wrong?