Formulas stopped working

[TomE]

I have a pretty basic spreadsheet that I've used for over a year now. I
don't recall doing anything different, but suddenly this week, the formulas
don't seem to work. They're still there, but they don't calculate a new
number when I change the cells they refer to. I'm sure this is a simple fix
- can someone point me in the right direction?

 

[Gary''s Student]

Formulas stop updating if the Calculation Mode has become Manual. To fix this:

Tools > Options... > Calculation > Automatic