In General > Misc. Info./Direct Deposit > Dir Dep/Elec Pymt have you entered

• Bank account information verified ✔️
• Electronic payment of tax due with extension ✔️
• Routing Transit number ########
• Depositor Account Number #######
• Type of account .... 2?

That should create the 8878

Maybe you checked the box for Electronic payment of balance due - What until you file to check that box.