How to generate ZAK token to Start a meeting in ZOOM

Question

I am trying to integrate the latest zoom SDK iOS(5.10.1.3038) in my application, Previously I tried to login using email and password along with meeting Id to start the meeting. I know that functionality is deprecated, So I am using the OAuth authentication also I want ZAK token to host the meeting, I tried to generate the ZAK token using URLScheme (PKCE) OAuth but Its not working. Also I tried using the API also to generate the ZAK token still getting error code as 4700. I have some doubt

1. should ZAK token be generated from mobile, If so anyone can please guide how to generate.
2. Should I authorize each time to start a meeting, if so which account should be used authorize our admin account has around 100 user should we use those or the personal account of the clients.

I referred this to generate the ZAK through API https://marketplace.zoom.us/docs/api-reference/zoom-api/methods/#operation/userToken

 //Sample for Start Param interface
MobileRTCMeetingStartParam * param = nil;

MobileRTCMeetingStartParam4WithoutLoginUser * user = 
[[MobileRTCMeetingStartParam4WithoutLoginUser alloc] init];
user.userType = MobileRTCUserType_APIUser;
user.meetingNumber = kSDKMeetNumber;
user.userName = kSDKUserName;
user.userID = kSDKUserID;
user.isAppShare = appShare;

user.zak = kZAK;
param = user;

MobileRTCMeetError ret = [ms startMeetingWithStartParam:param];