I was able to get it working. For those that may need to resolve this in the future, the answer was at this link: :backhand_index_pointing_right_light_skin_tone:

https://github.com/MMRIZE/MMM-CalendarExt3Agenda#update-to-120

When some submodule is not updated, try this.

cd ~/MagicMirror/modules/MMM-CalendarExt3Agenda
git submodule update --init --recursive