CAS : no matching login attempt found

Hello, I have an issue with cas connection.
I must use CAS connection because we have 2 domains, and rocketchat can only use 1 ldap domain at same time

Thank you

Description

“no matching login attempt found” popup message when attempting to connect with CAS.
URL are correctly configured: https://url/cas & https://url/cas/login
Cas connection works with other appliance like moodle

Server Setup Information

  • Version of Rocket.Chat Server: 2.4.7
  • Operating System: Ubuntu 18.04
  • Deployment Method: Manual
  • Number of Running Instances: 1
  • DB Replicaset Oplog:
  • NodeJS Version: v8.11.4
  • MongoDB Version: 4.0.16
  • Proxy: nginx
  • Firewalls involved: fortinet

Any additional Information

This is the only log i have when i try to connect:

I20200219-14:39:06.420(1) server.js:204 CAS ➔ error error when trying to validate: unable to verify the first certificate

Popup message: no matching login attempt found