When you hit $500 of FUTA liability within a quarter you are then obligated to remit a quarterly payment. Look at your payroll liability report for 1/1-9/30 and you will probably find that your liability exceeds $500 and thus needs remitted by 10/31 - which is a Saturday so the extended due date is 11/2. If you balance was less than $500 disregard the notice
At least your version of QB correctly identifies the payment due. Our desktop version (Pro 2020) did not. I made my payment to avoid penalties from teh IRS