Thanks for contacting the Community. I can certainly understand how this would be frustrating if certain transactions or periods are missing from the download.
Occasionally this can happen if there are connection faults with the bank account during the periods or potential background issues with the bank during the download times. It is for this reason that we always recommend double checking the periods to make sure there are no missing transactions from the download.
Don't worry though, there is a resolve for this. If you know the transactions that have been missed then you will be able to upload a csv file of the transactions though the QuickBooks banking page by clicking the dropdown arrow in the top right corner and selecting upload. You will have the option of either downloading a CSV file of your missing transactions from your banks website (You can select a specific date period or delete any transactions from the csv file to only show the missing transactions) or you could just create your own csv file on excel for the missing transactions (The Columns you would need would be, Date, Description, Amount).
While I do understand it is frustrating, this doesn't tend to happen often but we do always recommend checking your banking download to make sure there are no missing transactions. Our banking team does always try to work to minimise any disruptions but unfortunately these can still occur.
Please let me know if there is anything else I can help with and I will be back in touch. :)