Check
Tools | Options | [Calculate] tab and make sure that Automatic calculation
is selected?

"wicked2025" wrote:

When I type in a valid formula, a 0 appears instead of the result. If I copy
a formula from a different cell, the copied formula is correct, but the
result is the same as the cell I copied from.

Some setting seems to have changed on my spreadsheet that will not calculate
formulas.