Checking account does not balance

Good Evening

My checking account does not balance. It is overdrawn. There is an amount of 50 euros missing from it. The Balance is cleared according to the system . I have two other Savings accounts but they both balance according to Bank Account in Spain. Please can you advise where I can look for this error.
Thank You

It is not clear by “Checking account does not balance”

If you mean the account balance in Manager does not agree with the account balance on the statement received from the bank, then obviously, there is either a missing transaction in Manager or a transaction that has not yet been processed by the bank.

You will have to check transaction by transaction until you find the missing transaction

Or, of course, an existing transaction with different amounts