There's a reason nobody has ever done live streaming prices for free in a spreadsheet 👉 it's not* easy but don't worry we can help you. It also requires some additional steps for refreshing formulas and custom functions that have pricing feeds.
NOTE: while =CS.EXRATE in Excel is often the specific function causing problems, it can also happen with any other custom function
"WTF is going on? It was just working yesterday…?"
It has to do with how your authentication credentials are stored or 'cached' locally We only have so much control over it as Microsoft and Google maintain strict and complex authentication policies.
Steps to take
Log out then log back in
Refresh your add-in from the Excel or Googlesheets menus***
Check the side panel and web app to see if you're actually getting data by making a simple request
If you are, but still seeing errors in custom functions try these steps:
Select the cell with formula, press F2 then enter
Adjust your formula so it's using relative cell references
Then try changing each cell value (base, quote or refresh)
Try logging in using an incognito browser window
Try using the =CS.LOGIN("email","password") function**
Open the side panel click anywhere then press the F5 key for a hard refresh
Pat yourself on the back for getting this far