Firebase Function to use with 3rd party cron.

I have an iOS app using Firebase and there are items uploaded into the users Firebase Database that have dates needing to be checked daily against the current date. Using a 3rd party cron service, I'm trying to get a Firebase-Function to execute that checks these dates. However, I'm not having any success with the Firebase-function that I have written. I either need a working script written as a Firebase-function or a better suggestion of what to do in order to get this to work.