Hi, thank you for the feedback.
All files have the same problem and even If I open a new one. It won't work and I did the procedure you gave me, but still no success.
Here is my excel version and IOS.


I have just created a new excel file and wrote ddd and double clicked it on top to see if would auto fit, but no. I am also experienced using excel and this feature is something I use a lot, but for some reason it is not working.
Many thanks
Hi Danny,
We are more than willing to help you figure it out.
Based on my test, we can use AutoFit feature.
To clear the situation, I need to confirm if you have tried the following steps to check the result:
- Select all the column.
- Put the mouse on the border of the column.
- The following icon will occur:

- Then you can double click to use AutoFit.
If the issue still exists, could you please provide the following information?
- The OS version and Office version. (Click Excel>select About Excel)
- Check if all files meet the issue.
- Can you use it before? Which operation have you taken before the issue occurred, such as updating Office?
Regards,
Qing