Zach That is probably because you've added columns and the formulas in the spreadsheets are now missing the reference cell.
Have you followed the steps in this video? Please make sure you're only changing data in the spreadsheets and if you want to add columns you should do so on the far right. For example: In the "Check in" file, only add columns after Column E.
See also this video: https://www.youtube.com/watch?v=T0HLhTKZAB4&t=66s&ab_channel=Sheetgo