multiple connection l2TP behind a NAT

[qsdfg]

Hello all,
I am using a pfsense.
I configured an L2TP server with several different users.
However, I have a connection problem when I try to connect with several different accounts on a public IP address (behind a NAT).

By cons, I can very well make different connections in several different places.

Can you help me solve my problem please?

Regards