It is most likely because its either a weekend or banking holiday. Since ACHWorks does not process transactions on a US Banking holiday until the next day, MCA Suite does not send transactions over you have scheduled over to ACHWorks.
You can still schedule and send a payment, but it will be the following day's transaction.
For example, you schedule a debit transacation of $100 for November 27th and 28th where the 27th is a holiday. ACHWorks will debit the Merchant $200 ($100 twice on) November 28th because November 27th was a holiday.