Why are my formulas changing to text if I edit them in any way?

GerryVB  wrote: ``If I edit it to say =D1, the cell will simply read "=D1"``

To be clear, you are saying that the cell displays =D1 even when the cell is not selected, not just in the Formula Bar.  Right?

If so, you probably formatted the cell or column as Text after you had entered the original formula, =C1.

Select the cell or column, and format it as General (or any other numeric format; not Text).

It is not necessary to format a cell as Text if a formula returns text.

And it does not help to change the format of a cell format to Text after you calculate a numeric result.  The type of the result remains numeric, despite the cell format.

The only time that we should format a cell as Text is when later, we enter data that we do not want Excel to interpret as numeric or a formula.