ONLY the Microsoft Customer Service team will be able to supply the code needed, so searching and asking on the internet is not going to get you the numbers you need.
No activation code is needed, that's for desktop versions of Windows. Just put in your sim (assuming the phone is not locked to another provider, in which case you'll need to pay to have the phone unlocked) and away you go.
ONLY the Microsoft Customer Service team will be able to supply the code needed, so searching and asking on the internet is not going to get you the numbers you need.
Wow, I never knew that. How annoying, because once this fault has been triggered it seems you're permanently stuck with a manual entry code work around, no way to restore the phone's original code.
I would love to know why this happens so I can avoid triggering the error. Also, just in case, is there any way we can read the activation code in our working handsets so if it does get wiped we can feed it back in again? Using the original code may avoid having to feed it in at every reset so it would be worth keeping a record of it somewhere.
The original code is worthless, no point looking for it. It is not "lost" - it is stored in a non-writable area of the phone and is unique per phone.
What happens is every time the phone is "activated" after a factory reset or flash - by associating it with a MS account, it uses up one activation. Trouble is, the number of activations available per code is an unknown number, and once it's reached zero you need a new code.
My speculation for why it's there in the first place: the codes are issued only by Microsoft so they know OEMs can't exceed the number of phones they have obtained a license to build. But why this code would have a limited number of uses, who knows - unless it's to prevent an OEM from using the same code in every phone?
Weird. Why on earth does this not work like the desktop version of Windows? If the code gets blocked for some reason a call to MS reactivates it, it doesn't need a new code. Also you can reinstall on the desktop as many times as you like, and even move a retail edition to another PC, with no faffing at all. This weird policy on the phones can't be necessary. Are OEMs really likely to think they can get away with putting pirated editions on phones without having the licences blocked?
The lesson from this is that you don't reset your phone unless you absolutely have to. It is very nasty for MS to hide the number of activations from us, because it means any reset could be the last for the embedded code meaning you have to contact MS support who seem to just accuse you of having a virus ~50% of the time, whatever the problem. I hope W10 fixes this little trap.
I said it is an unknown number but I expect it's a pretty big number. With the several phones I've been using for testing Win10 and my various debranding and other experiments, I would have expected to have this problem eventually but haven't seen it yet.