I took these steps to fix the problem:

1. Open the ios folder of your flutter project in Xcode

2. In Xcode click on "Runner" ( Ensure that the "Runner PROJECT" and not the "Runner TARGET." ).

3. Duplicate a "Release-Production" Configuration :

   • In the Xcode menu bar, click on Editor.

   • Hover over Add Configuration.

   • Select Duplicate "Release" Configuration.

4. Rename the Duplicated Configuration:

   A new configuration named "Release-Production Copy" will be created. Rename this new configuration to simply "Release."

5. Now you can retry building the IPA, the command should work just fine now.