The most common explanation for the difference is that there are unreconciled transaction in Ember. For an explanation on how to reconcile your transactions, please see the article here.
If you have no transactions to review, one of the main reasons why your bank balance in Ember would differ to your bank statements may be due to the transactions being pending. Some banks will create the pending state and remove the balance from your account, so that you are unable to spend it. This would only push through to Ember once it has been confirmed.
The first thing to check is that the missing transaction is confirmed with your bank. Once it has been confirmed, it should show within your transaction in Ember.
If it has been confirmed, then please contact support so we can look into this issue further.