This one hits close to home.
My wife and I bought an 2014 bmw i3 from a repo auction.
Once I got the car home and hooked up to Ista +, I saw that the VIN in the BCM differs from the cars VIN on the frame and paperwork.
It appears that someone has swapped in the BDC from a different i3 and didn't code in the FA or register the correct VIN to the BDC.

We managed to code the right vin to the BDC and straighten out the FA. But the car will not move , IMMO is activated I believe with an error.
21E921 electronic Immobilizer: non authentic response received.
what to do in order to get the ISN (I presume) in the eDME changed to match the request from the BDC?

Or what do we need to do in order to remedy this?
thank you, and I know its a deep dive for a first introductory post.

You have to match EDME and BDC ISN to start the car. Please read the EDME ISN with Autohex (ISN Manager --> Option 1) on the car with ignition ON. In some cases, the EDME may need an update to read the ISN.
Then write this ISN to the BDC using ISN Manager --> Option 4.

To write the ISN, unlock the BDC with a working key option. If no key is available, unlock the BDC on the bench with the 'no key/no ISN' option, then program a key(key learning --> option 2) afterward to switch the ignition ON and read the EDME ISN on the car, then write it to the BDC.