Calculator Percentage Button Not Working

I used to be able to calculate a percentage off by typing in the number then hitting minus then the “percentage off” number then tap the percent sign and it would show me how much off and then I could hit equal for the cost.

I.E. - 100 - 20% (it would then calculate 20) and then I could hit = and it would show 80 as the total.

However when I try to tap the % button it does nothing now. I have tried restarting my phone. Has anyone else had this problem and if so, how do you fix it? I use this function a lot for my business and really don’t want to have to download another app to use this function. Thanks!