Basically selling digital delivered items and buyer has gone to credit card company and issued a chargeback, now paypal are asking me for more information.
And that's why I stoped selling digital delivery items... no protection. Saying that chargebacks are something you have to try and factor in but its a pain in the ass..have you tried contacting the buyer? If not I don't think there's alot you can do my friend.
Can you not send a copy of the code to the buyers address now via recorded delivery? When he signs you have proof of delivery. In fact you may only need proof of postage against chargebacks, however I cannot remember exactly. Sure it will cost a £1 or so but its better than losing out on the money.