The #REF! error shows when a formula refers to a cell that’s not valid . This happens most often when cells that were referenced by formulas get deleted (typically deleting tabs or deleting columns), or pasted over. 
#REF! errors will likely cause "Update Data" and "Create Powerpoint" to fail.

Here's an example of how that looks in the tab from a DRT:

Here's an example of how that looks in the formula bar:
 

It is unadisavable for you, or even Josh, to attempt to fix the #REF!. It is both painstaking and error prone to do this. It is better to backtrack, step-by-step, until you have a version that works again. 

  1. If the #REF! occurred because you have just deleted columns, you can attempt to undo. (CTRL + Z)
  2. If you haven't saved, you can close this version and reopen the file before you last saved.
  3. You can use Google Drive's "Manage Versions" to revert back to a previous version
  4. You can start over from the previous month's file. For example, you can restart the Febraury file with the January one.
  5. Finally, you can go all the way back to the original template.