There are many reasons why your Google Sheet Widget might not be functioning properly. From adding an incorrect API key to adding a false Value Range by not using proper A1 Notation. If those values are correct, you could be running into a quota limit.
Unfortunately Google defines a quota of 500 requests per 100 seconds for each API key. This sounds a lot but if you are using multiple Google Sheet widgets in a single Composition, you could hit this limit. In these cases, Google prints tons of error messages in the console indicating the issue. Try to limit the number of times you use a Google Sheets Widget in a single Composition to limit the amount of requests per 100 seconds to the same API key.