Trying to sync new iPhone 7 plus with an iTunes backup from old iPhone 6. iTunes says my password is incorrect. What password is this? I have been typing in AppleID password.

The device's backup was encrypted and a password was set. Here are some screen shots and a full article explaining. Without the password there is no recovery option. It is not your iTunes password. It is a separate user created password. Hope this helps.

About encrypted backups in iTunes - Apple Support

And Apple may say we're wrong but I have had this issue with my Facebook password. I've let keychain auto generate a password. Later it tells me the password is incorrect. Sorry Apple, but this is the honest truth.

How is your issue with a auto-generated Facebook password relevant to this conversation?

With an iTunes backup encryption password, you must enter it twice. The dialog also directs you to keep it safe ands clearly explains the consequences of not doing so.

Yes, you are given the option to remember it in your Keychain, but that is at your risk. Software based keychains can be lost, damaged and are a smart part of a password strategy, but not the entire strategy.

About encrypted backups in iTunes - Apple Support

This is also the honest truth.

It sounds as if your iTunes backup was encrypted. You would have had to set an encryption password if, for example, you wished to save health data.

About encrypted backups in iTunes - Apple Support

UPDATE - Sorry, I did not realize I was not the first person to respond. Did not see all the above posts except the original.

Well. Here is the PART of the question which I answered. I comprehended the entire question. Apparently y'all are only seeing the original question. I responded to a followup.
Good day sir. I will only respond to the original poster from this point forward.

This is a backup encryption password, it is different from your Apple ID password. You must have set it when backing up your old iPhone. Unfortunately there is no way to recover this if you have forgotten it.

I am trying to restore an encrypted backup to a new iPhone 7+. Old backup was from a 6+. I saved the encryption password in my keychain. I understand that this is not my Apple ID password and is a specific password for the encrypted backup. When I try to restore the backup, it asks for the password and keychain inputs a password as it should. However, iTunes then says this is the wrong password. I enter it manually, still says it is the wrong password.

Anyone seen this???

Honestly yes. And Apple may say we're wrong but I have had this issue with my Facebook password. I've let keychain auto generate a password. Later it tells me the password is incorrect. Sorry Apple, but this is the honest truth.

The question was.....has anyone else had this issue with passwords. My answer was relevant. Keychain is an Apple product also. Therefore I offered my experience. It was NOT an opinion. It is fact. You are free to disagree if you wish.

The question was.....has anyone else had this issue with passwords. My answer was relevant. Keychain is an Apple product also.

That belongs in a net new discussion about Keychain and Facebook.

You are free to disagree if you wish.

As are you.

Steve67_ wrote:

So your opinion is that I'm not allowed to answer the question. You feel the need to pick an argument. Your reply belongs in the temper tantrum forum.

It is considered bad form to make a post unrelated to the original question. There's even a name for it "thread jacking". Also, it decreases the likelihood that you will get the help you need. That's why it was suggested that you start your own thread.

Steve67_ wrote:

I answered the question. They asked if anyone else had had this similar issue with passwords in keychain and I said yes, with Facebook.

Really? Here is the question:

lemiller16 wrote:

Trying to sync new iPhone 7 plus with an iTunes backup from old iPhone 6. iTunes says my password is incorrect. What password is this? I have been typing in AppleID password.

So I would draw a different conclusion about your response, and it would agree with IdrisSeabright

To LACAllen and Steve67 - I am currently unable to backup a phone that crashed and is now offering to restore from icloud, iTunes or reset as new - it is incredibly frustrating because I think I have roughly the same issue as reported here, the password that I know is currently right is being rejected by Apple. - Apple appears to want the original password when I set up the phone - but that was eons ago and because Apple keeps asking me to update my password, I no longer remember that original one. This doesn't make any sense to me. I use the finger touch security which is likely way more secure than what they suggest "write it down or you won't be able to back up" - it never occurred to me that when I updated the passwords, it wouldn't automatically update the restore password. This seems poor engineering..... why on earth wouldn't the restore password back up too. And if Apple really wants an ancient password, for goodness sake give us plenty of times to get it right, which of course isn't very secure...... Please don't make our lives more complex with even more codes...

Sarah C-S wrote:

it never occurred to me that when I updated the passwords, it wouldn't automatically update the restore password.

That password for the encrypted back up is not linked, in any way, to any other passcode. This is just like your Apple ID password is not linked to your iPhone unlock passcode. Having passcode for different functions linked in the way you assumed they would be is poor security.