I experienced the same issue with the MP808TS on the 2007 Infiniti G35x. It could read the BCM code after which I was able to generate the PIN. However, it returned an error with both the old and new PIN and I couldn't proceed.

 I don't think having the AP200 bluetooth dongle versus the cable of the MP808TS made any difference in requirement of having to entering a PIN. It might have been the difference of one tool having an active update subscription and being able to retrieve what it needed from Autel's server and the other tool wasn't able to connect to it , so it asked for the PIN.

  Well, the MP808TS had an active subscription but failed to read the PIN or even ask to be connected to the internet. NATS all keys lost procedure makes it risky to engage in key programming and Autel needs to do something about it.

 It’s a software issue, I can duplicate it easily on my IM508 by selecting an incorrect model year when adding the intelligent keys. The software is outdated and without proper warnings.

I am also having issues with programming the ikey
And getting the pin code

  What tool are you using? If it’s an MS series tool and not a IM series and the Nissan is over 2007 it’s a software issue. They are not building the IM software into the MS in full support anymore. Same deal as when the tpms tools were launched, stripped it out of the MS series. Discovered the hard way that using anything but my IM machine instead of my MS906 over an 07 makes nice 4 wheel bricks. My favourite part was how you can delete the keys then never re add them even with the proper access code. 

 I got same issue with ms906ts . I called tech support wich was the worst experience ever ... The guy was rude and basically told me my scan tool could not do it . I try multiple thing and if you go through the third function'' Installed remote start'' something like that and choose first option after without cable follow all the instruction and it will work . I had car stock on the hoist and customer waiting I was going to buy a new scan tool but my old 906ts still in the game !!

 We have the same problem on our 906BT, we tried it on 2 different infinities (2006 and 2009), both times it failed. It just erased the customers old keys but wouldn't add the new ones. Just says Failed To Complete The Operation. Wasted our time and money, left us with a totally inop car we couldn't give back to the customer. We had to call in a mobile locksmith to add the customers keys back on. 

If the options does not work, they should remove that feature from the scan tool. 

We have a current autel subscription and there are no system or infinity / nissan updates available. 

Same issue, mp808ts, 2009 g37. Use remote engine starter install instead and worked.