Google Sheets Strikethrough Conditional Formatting

Hi! I am trying to format where with a checkbox, it will strikethrough on the next cell. I had it working, but now it is not. I used, "=$B$23=TRUE" and then changed the format to strikethrough. It stopped working. Can someone help. I am trying to do it for the calendar and the to-do list.

Link: https://docs.google.com/spreadsheets/d/1uvswiwEasQ7ZyQwdyEp6Ux3fFMihipYmb4GjWSdUjUc/edit?usp=sharing