When you're starting out in the editor, you're first going to add at least one table. However, as you're working with your data in the editor, you may realize you need to make changes to your spreadsheet. You may decide you can get rid of a column, or maybe add a column. Then, you run into something like this in the emulator:
Here's how you resolve the problem.
Let's say this is your original spreadsheet; you have these three columns:
Then, you decide to add another column in your spreadsheet:
In the Data tab, go to the columns section and find the table for which you just made changes.
Then, select "regenerate":
Then, select "regenerate".
When you sync in the emulator, you'll now be able to see your additional column in whatever view(s) you have set up.
Remember to regenerate your columns whenever you make changes to the number of columns you have in a table.