Great points to the most common reason bank transactions cannot be matched, but there is still one possibility that causes transactions to not show up to be able to match to bank transactions. If there are any discounts or adjustments or other reason that causes the sales receipt/invoice to be higher than the bank deposit amount, it will not show. When you go to the matching screen.

The reason is when you try to match transactions, QBO will only show sales receipts/invoice transactions that are equal to or lower than the amount of the bank transaction you are matching. So even if your bank account is right, time frame is right, hasn't been matched yet, it still will not show up no matter what.

Currently I cannot find any workaround besides manual adjustments of the sales/invoice amounts.

QBO, please enable amounts larger than the bank transaction to show when we try to match bank transactions.