this is because of the new regulation rules that Chinese exchanges have to follow now. and since you said it is a large amount they are asking for more information. he has no choice but to provide all these documents properly and fully.
he is doing something wrong that they are rejecting his docs, just tell him to contact the site support and solve it by communicating.
Its almost the same thing as this guy here:
https://www.reddit.com/r/btc/comments/6g8rd8/okcoin_is_robbing_me_for_97_bitcoins/?sort=confidenceBtw, he is in contact with support for a month, but i think theres a lot of people with the same problem and the support is not enough to handle everyone, thats why its taking so long.
And even tho he has a large amount, its not the problem since he cant even withdrawal even 0.1 btc lol. His compliance level is zero now. He need his docs to reach lvl 1 and be able to withdrawl 10k usd in bitcoin
unfortunately this seems to be the new rules as i said above combined with the massive ticket requests and their lack of enough support power.
if the amount is big like that guy in the reddit link you can tell him to make a topic on reddit and ping those /u/okcoin... guys that were pinged in that comment below it. and since it is already 1 month i think it is ok to do it now.
i already created a post on reddit, but its not getting many upvotes, so i dont think many people will read it.
Anyway, thats unacceptable that okcoin is doing that almost from nowhere since like 2-3 month ago we could withdrawals as many btc as we want and now we can even withdrawal a single 0.001 btc? (btw, today we are having problem with chinese exchanges, but we don't know whats gonna happen tomorrow and maybe EU and USA exchanges will do something similar)
I hope they solve everyones problem and dont steal (lock) bitcoin from investors.