How to set up connection to VPN L2TP server on Windows Server 2012 with iOS client?

Question

iOS

Hello!
There is a configured server with Windows Server 2012, the RAS role is configured on it, the VPN server service (PPTP + L2TP) is running, Windows clients and the mikrotik router connect both via L2TP and PPTP.
I'm trying to set up an L2TP connection on an iOS client (iPhone 7, iOS 12) and I get an error

. From the same phone, I can easily connect to two other VPN servers (both servers are hosted by mikrotik) via L2TP.
Apparently something with setting up a VPN server on Windows Server, what needs to be configured to connect iOS clients?
Do I need to change the AssumeUDPEncapsulationContextOnSendRule / ProhibitIpSec / AllowL2TPWeakCrypto values ​​in the registry?

Answer 1

The solution turned out to be simple, but it took 4 months to find it.
My shared password contained the characters ., - as soon as I removed them, the connection immediately worked.