Due to the bug in the Windows May 2019 Update (1903) which is the latest version, we confirmed that the screen to enter your ID and password for IKEv2 ID/password connection is not displayed.
We have published its workarounds the link below.
If you cannot connect IKEv2 in Windows 10, please refer to it.
http://www.iimc.kyoto-u.ac.jp/en/faq/network/vpn/windows_10_1903_ikev2.html