As we can’t see the reports, all we have is the two figures you are quoting - an answer can’t be provided based on those quoted figures.
Is your P&L statement cash or accrual basis ?
Do both reports have the same starting date ?
Does the P&L Sales include non-inventory sales ?
You could create the reports over a shorter time span - Start of year + one week, then two weeks etc which will make it easier to analysis any differences .