Unfortunately, when you merge cells and then choose the wrap text option, the Autofit function won't work as expected. This is because Excel treats merged cells as a single entity, and the Autofit function only works on individual cells. However, there are a few workarounds you can try to get around this issue.

1. Use the "Center Across Selection" option instead of merging cells: Instead of merging cells, you can use the "Center Across Selection" option to center the text across multiple cells. This will allow you to use the Autofit function on each individual cell, and the text will still appear as if it's in a merged cell. Here's how to do it:
   
   - Select the cells you want to center the text across.
   - Right-click on the selection and choose "Format Cells".
   - In the "Alignment" tab, choose "Center Across Selection" from the "Horizontal" dropdown menu.
   - Click "OK" to apply the formatting.
   
2. Use a formula to combine the text: If you need to merge cells for a specific reason, you can use a formula to combine the text from the merged cells into a single cell. Here's how to do it:
   
   - In a new cell, type the formula
   Formula:

   "=A1&" "&B1" 

   , where A1 and B1 are the cells you want to merge.
   - Press Enter to apply the formula.
   - Copy the formula down to the other cells in the column.
   
   This will combine the text from the two cells into a single cell, which you can then use the Autofit function on.
   
3. Use VBA code to Autofit merged cells: If you're comfortable with VBA code, you can use a macro to Autofit merged cells. Here's an example of the code you can use:
   
   
   Formula:

   Sub AutoFitMergedCells()
   Dim cell As Range
   For Each cell In Selection
       If cell.MergeCells Then
           cell.MergeArea.WrapText = True
           cell.MergeArea.Rows.AutoFit
       End If
   Next cell
   End Sub 

   To use this code, select the merged cells you want to Autofit, and then run the macro. The code will loop through each cell in the selection, and if it's a merged cell, it will set the "WrapText" property to true and then Autofit the rows.
   
   I hope one of these solutions works for you!