"Cannot query internal supporting structures" error

Hello, all. I'm using the web app of Power BI (data is in a OneDrive for Business/Sharepoint Excel doc), and everything has been working smoothly, when all the sudden I'm getting this error:

"Couldn't load data for the visual. 

Cannot query internal supporting structures for the column 'Satisfaction S18'[Coach's name:] becuase they are not processed. Please refresh or recalculate the table 'Satisfaction S18'."

Technical Details:

I'm confused because the column in question is a list of names; there's nothing to "recalculate." I'm not sure what's going on, but any help would be wonderful: 

Solutions I've already tried: 

1. Adding more data and triggering a refresh

2. Copying/pasting all data into a new excel document with the same file name (trying to "clear out" weird formatting)

Thank you!