My formula shows the formula text instead of the result — cell formatted as text
You type =A1+A2, hit Enter, and the cell literally shows "=A1+A2" instead of a number. That's not a calculation setting — the cell was formatted as Text before you typed the formula, so Excel stored your entry as a text string rather than something to evaluate. Drop your file in below to see which cells this affects.
What's actually going on in the cell
Excel decides how to interpret what you type based on the cell's number format at the moment you type it. If that format is Text, an entry like =A1+A2 is stored character-for-character as a string, equals sign included, and displayed exactly as typed — left-aligned, like any other text. Excel isn't ignoring the formula or refusing to calculate it; as far as the cell's stored content is concerned, there is no formula, just a string that happens to start with an equals sign.
Why reformatting the cell after typing doesn't fix it
Switching the cell's format from Text to General or Number after the fact changes how a new entry would be interpreted, but it does not retroactively reinterpret content that's already sitting in the cell. The stored value is still the literal text string — Excel needs to actually re-parse the entry, which only happens when you re-enter it.
Where the Text formatting usually comes from
This is common in columns that were deliberately set to Text earlier to preserve leading zeros or prevent auto-formatting (see: phone numbers, ZIP codes, SKUs), and then later reused for a calculation without anyone changing the format back first. It also happens after pasting data from a CSV where the whole column import type was set to Text.
How to fix it
Select the affected cell or column, change the number format to General (or Number), then for each already-typed formula, click into the cell and press F2 followed by Enter — this forces Excel to re-parse and evaluate it under the new format. For a whole column at once, Data → Text to Columns → Finish also forces re-evaluation without retyping each formula individually. Upload your file above to see which cells are currently text-formatted so you know exactly which ones need re-entering.