The two reports aren't expected to match.
They would only match if:
1) All of your income is recorded on invoices. No other transactions in your entire company file use income accounts.
2) Every line item recorded on invoices is linked to an income account.
3) The reports both use the same cash/accrual basis.
Maybe.
You can see what's behind the numbers on your Profit and loss by clicking on the numbers there to open a detail report. Or, run a Detail Profit and Loss report.