This KB explain how to connect to ACX7024 console

Below are the steps to be followed for console connection.

• Verify that the following default serial port settings are configured on your laptop or desktop PC:
  • Baud Rate—9600
  • Flow Control—None
  • Data—8
  • Parity—None
  • Stop Bits—1
  • DCD State—Disregard
• Connect the console port on the ACX7024 or ACX7024X to a laptop or a desktop PC using the RJ-45 cable and RJ-45 to DB-9 adapter. The console (CON) port is the lower RJ-45 port on the left side of the port panel. 
• At the Junos OS Evolved login prompt, type root to log in. You don't need to enter a password. If the software boots before you connect your laptop or desktop PC to the console port, you might need to press the Enter key for the prompt to appear.

NOTE: If your laptop or desktop PC doesn't have a serial port, use a serial-to-USB adapter (not provided).

If the console is working even with initial settings, pls follow below steps

• Test the console cable in another equipment & confirm its good one
• If cable is tested good, pls restart (power-cycle) the whole chassis
• If its still not working, we may need to replace the chassis

Below is the public document detailing these steps

https://www.juniper.net/documentation/us/en/hardware/acx7024/topics/task/acx7024-initial-configuration-cli.html