[kamocat]

I reinstalled the FRC Core software, and now the default project works.
My modified project still doesn't work when deployed as startup.
(I'm using the term "works" here to mean that the DS recognizes the code on the robot, as opposed to the non-working condition where it did not.)

Just out of curiosity, I created a VI and only put the StartCommunication.vi in it, created a real-time deployment, built it, and deployed it as startup. (This was done in my modified project.)
Just like with Robot Main, the DS connected, but wouldn't recognize code.

Now, I did the same thing with the default project, and the driver station connected and recognized code.