iOS IPSec Remote Access Connection Failure after SFOS 17.5.3 (MR-3)

Hi, I have a configuration in the "Sophos Connect Client" tab and iOS profile that allow users (who are with iOS or Mac devices) to connect VPN to XG on demand, and it works fine with SFOS 17.5.3 (MR-3) and before SFOS versions.

However, after upgrading to later SFOS versions after MR-3 (I tested the MR-5, and latest MR-8), both iOS and Mac OS devices cannot connect to the IPSec ("Sophos Connect") VPN, it only works fine after falling back XG firmware to MR-3. 

I understand I should use the "Sophos Connect Client" application, but the problem is, it does not support iOS yet. And I tried to search the community but not much discussion about this issue with 17.5.

So, I would like to know, 

1. What is the ultimate solution(s) for iOS devices with the "Connect to Demand" feature?

2. What information should I provide for troubleshooting this issue?

Troubleshooting Steps (in MR-5 and MR-8):

1. Changed the Authentication type from Certificate to Pre-shared keys, and configure a new IPSec connection in iOS for testing, still fail. 

2. Tested in both iPhone and iPad, with iOS 12, iOS 13 and iOS 13.1, same result. 

Thanks.