Hello there! There's two likely reasons this could be happening. The first is that your server isn't updated to version 72 just yet, which you can check in the top-right corner of the WHM interface.
If you are at least running version 72 can you check for the presence of this touch file?
/var/cpanel/disable_whm_terminal_ui
That disables the terminal application from showing up in WHM even for root users. If that file is present you can just delete it and I would expect the application to show up properly in WHM.