Hi there! It sounds like your Excel settings may have changed recently. By default, Excel is set to automatically recalculate formulas whenever a change is made to the worksheet. However, it's possible that this setting has been turned off.

Here's how you can check and change this setting:

1. Click on the "File" tab in the Excel ribbon.
2. Click on "Options" in the left-hand menu.
3. In the Excel Options window, click on "Formulas" in the left-hand menu.
4. Under the "Calculation options" section, make sure that "Automatic" is selected.
5. Click "OK" to save your changes.

If this setting was already set to "Automatic", there may be another issue at play. It's possible that your worksheet has become too complex for Excel to handle and is taking longer to calculate. In this case, you may want to consider simplifying your formulas or breaking your worksheet into smaller, more manageable sections.