Why does Fishbowl say "The cost cannot be a negative amount."?

The system won't accept a negative cost value. This usually happens when you enter a cost as negative or when a calculation produces an unexpected negative result.

Fishbowl: 'Cost cannot be negative' — Israel Lopez Consulting

What it means

The system rejected a cost field containing a negative number. Fishbowl requires cost values to be zero or positive. This typically occurs when you manually enter a negative cost or when a formula generates one.

What to check

Is the cost value actually negative? Verify the number you entered or the source of a calculated value.
Are you trying to apply a discount? Use a discount field instead of entering a negative cost.
If this appeared on a computed field, check the source values feeding into the calculation.