Microcontinent Issue with Plate IDS

Hey. Like most of us, I’ve been following along with Artifexian’s tutorials for constructing my world’s tectonics, and, like most of us, I’ve run into an issue - my first attempt at a microcontinent isn’t showing up in my ‘Equivalent Rotations rel. Anchored Plate’ tab.
At 850 MA, I’m trying to split the newly created 501 microcontinent from the 500 continent. Yes, I’ve set the anchored plate ID to 500 and this is the following code in my rotation file:

501 0.0 90.0 0.0 0.0 000 ! micro end
501 850.0 90.0 0.0 0.0 000 ! Move indep.

Everything seems fine (and lines up with the video tutorial) until I hit command P and the 501 plate ID doesn’t come up for me to get its coordinates.
Any help would be greatly appreciated.