Why is a row of buttons on my TI 84 plus not working?

I’ve got a TI 84 Plus in good condition; the only problem is that not all of the buttons work. Specifically the buttons that aren’t working are the “log”, “7”, ”8”, “9”, “x (multiply)”, and the Up button on the keypad. The first 5 of these buttons are in a row straight across the keypad. I’ve tried cleaning the key mat and the big green motherboard, still nothing. There was some yellow gunk on the board when I cleaned, there might have been a battery leak at some point maybe? Any help would be very much appreciated!