Earphone jack not appearing in system prefs.

My daughter has this problem where she is using her Aux. cord to add audio to her sound system to watch movies using an HDMI in tandem to her TV set up. She has recently encountered a problem where the sound won’t work through the earphone jack anymore. She’s tried inserting it in and out, turn and twist and even went to systems prefs and didn’t even see the option for an output via earphone jack. The only thing that works it the external speakers on her MacBook Pro. I have a suspicion the earphone jack is blown and the only fix is buy another motherboard as this is irreplaceable otherwise. Any suggestions and insight would be greatly appreciated. Thanks!