A payment I marked as received is not showing on the system!

The most common cause for this problem is that the payment receipt has been recorded with a date prior to the property's opening balance date.

If you enter a transaction with a date prior to the property's Opening Balance Date, such as a rent received or a sundry fee, then it will be ignored.

You should identify and delete the relevant transaction via Reports > Bank > Tenant Transaction Report, then reenter the receipt with the correct date. Or alternatively update the opening balance date if that is more appropriate.