MikroTik L2TP-IPSec server: phase 2 establishment error - how to treat?

Question

Mikrotik

Good afternoon!
I wanted to set up an L2TP / IPsec server on a working MikroTik router, when I try to connect to it, Windows writes that the connection is impossible, for the probable reason that there is a firewall on the way. Incoming ports for L2TP, IKE and esp protocol - dug in advance. I began to read the Mikrotik logs, where he reports that the ISAKMP session (phase 1) was successfully established, but it was impossible to establish phase 2. I found out that this was due to NAT, but no attempts to enable NAT Traversal helped. Can you tell me where to dig and how to defeat it (if possible)?
Thank you.

Answer 1

Well, ideally, look at the log.
Second, the provider can block l2tp. (Extremely rare, but there is)
But let's start with the logs.