Dave works with 3rd party companies like Plaid.com who allow us to access data on behalf of all of our bank partners.
Traditionally, banks have not had a reason to send real-time updates to companies like Dave who want to help customers manage their money more effectively. It is often a struggle and those data feeds can be delayed which is why your transactions will not be updated. This generally will happen more on weekends and mostly with Chase Bank.
Rest assured we are constantly checking to see if new data is available and we apologize for any delays.