According to TIR 15-15, extensions are granted automatically if 50% of the total excise has been paid by the original due date. Only file Form 355-7004 if a payment needs to be made to satisfy the minimum 50% requirement for the automatic extension. Massachusetts doesn’t accept e-filed extensions without payment. Refer to TIR 15-15 for additional information.
For processing payments through the website, you may try removing the debit amount to see if it qualifies, as the system only supports Direct Debit for e-filing. Alternatively, you can paper file the return and pay through the Massachusetts website via EFT. When the Tax Payment Method is grayed out, there is no option to select a different method other than Direct Debit.