In the TurboTax (2023) Desktop app, I completed my tax return, went through all the reviews/checks and proceeded to eFile my return. A day later I got an email saying it was rejected. The reason was because I had not entered my IP PIN - which I didn't know I needed, and didn't know where to enter it.
The app should not have let me complete the eFile step without that IP PIN, as it is required.
On an unrelated topic: the "Choose The Platform" selection on the form where I created this forum post doesn't have enough options. It only has "Online", "IOS", and "Android". My desktop version of TurboTax doesn't fall into any of those categories, so I had to select "I Don't Know". Just sayin'.