Simple Excel--WHAT has changed in new version?

Thank you. I started with =A12+B12. Also makes no difference if use + on keyboard or number pad. Have same issue with =A12*0.18 returning 0 while entering the value of A12 works, which is simply calculation of 2 numbers, not a calculated cell. Found a previous discussion by Minizv on July 13, 2022, with basically the same question and no solution.
I have the computer-based Home and Student version and get the message that my administrator has turned off the Help feature. I am the admin and did not turn it off???