Casio PX750 not allowing midi note entry

I am using MacBook Pro with 10.7.5 operating system with a Casio PX750 keyboard.

I have MuseScore version 1.3. MuseScore appears to be recognizing that the keyboard is connected.

I am trying to set it up for midi note entry for the first time. I have watched/read the applicable handbook entries and video tutorial. I have double checked the following per the handbook/video tutorial instructions:

"Enable Midi Input" is turned on.

"Casio USB Midi" is showing as the input interface.

"Enable Sound While Editing" is turned on.

I have been connecting the computer & keyboard in the following manner:
Connect to computer with USB cord.
Turn keyboard on.
Open MuseScore.

Problem: No note entry occurring when I select a measure and switch into note entry mode. I have tried closing and restarting the program. I have also tried disconnecting and then reconnecting the keyboard. Still no note entry.

Has anyone else had a similar problem and figured out what the fix is?

Thanks in advance!