Iphone 8 plus asking for a 6 digit passcode that I never created

Unfortunately if you can’t recall the passcode, you need to restore it and then reload your most recent backup. See here: https://support.apple.com/en-us/HT204306

This happened to my iPhone last night, I was going to make a call and out of the blue it asked for a 6, not 4 digit passcode!

I explained this above. In iOS 9 (as I remember), Apple introduced six digit passcodes. Yes, the request to change it from four to six does pop up on its own. Normally, on the lock screen. You DO have a way do dismiss it. The text to skip isn't very big and is easy to miss. But, that still leaves only two options:

1. Press skip and keep your current 4 digit passcode.

2. Enter a six digit code. REMEMBER IT! Your old code will no longer work since you have voluntarily set a new six digit code.

No, I didn't like that this prompt would come up on its own, either. But you did have a choice. And entering a new code made it your responsibility to remember the new number.

It's you money, spend it however you want. But you can't blame Apple for something they couldn't have possibly done.

I do remember on my previous iPad that when a 6 digit code was introduced, you were asked right away at the lock screen to enter one. You did have a way to skip it, but if you entered one, that was your new code and you'd better remember it.

Even after setting up a new 4 digit one. It is asking for the old 6 digit passcode and it won't allow my wife's iCloud account to activate on the phone till someone comes up with it.

Again, this is not the 4/6 digit passcode being asked for. It is a separate code that was set up.

It can be reset.

See >>> Get help with iCloud Keychain - Apple Support

Somebody had to have changed it. It requires multiple steps to change and confirm. That can't happen on its own.

This happened to my iphone last and just to clear this up for the guy blaming your wife. I was holding my phone in my hand just last night and a screen popped up asking for a six digit passcode when I have had the same four digit passcode forever. And this came without my prompting, I was watching my daughtet skate and it happened without me even touching the screen. YES THIS DOES HAPPEN AND NO THE MAN'S WIFE IS CORRECT. THIS HAPPENED BEFORE MY EYES AND I AM FURIOUS WITH APPLE. IM TIRED OF HAVING MY INFO AND PICS, EVERYTHING WIPED! (Two years ago the lady at the genius bar wiped my ipad all by her genius self!) This is the last straw, I went from loving Apple to no more!

This happened to my iPhone last night, I was going to make a call and out of the blue it asked for a 6, not 4 digit passcode! I went into Apple and the same old story, we can wipe and restore it. No thanks, I'm done with Apple products.

I have the same problem as well. I don't use a 6 digit passcode, in fact it asked me for one last night so it could update overnight. I didn't type one in and figured it wouldn't update. I was wrong. It updated without me typing in the 6 digit passcode.

IF YOU ARE UPDATING TO IOS12 MAKE SURE YOU KNOW YOUR 6 DIGIT PASSCODE!!!! If you're reading this you are probably too late. I try guessing my password but forgot as I never use it. Then it locks me out for one hour after every try. I'm done with apple. Sorry, don't have 6 hours to spend trying to get into my phone only to have to reset the whole thing using a 3rd party app.

Really disappointed apple didn't think this one through more.

I have seen other posts like this, but no one can figure out how that can happen on its own. It takes a fair number of deliberate steps to change the passcode.

after entering the username and password for the apple id it pops up asking me for her old 6 digit code!?

That sounds more like iCloud keychain. Completely different thing.

See >>> Set up iCloud Keychain - Apple Support