Good day to all!
I have a problem with SoftEther VPN Server. The problem is that the clients do not want to connect. The Android phone simply fails with standard clients, and the built-in Windows 7 client gives an error # 789, the L2TP connection attempt failed due to an error that occurred at the security level during negotiations with the remote computer. UPD ports 1701,4500,500 on the server open server on Debian 9 VPN server downloaded from here https://github.com/SoftEtherVPN/SoftEtherVPN_Stable.git.
Where can I look for a problem?