First, if you generate .ipa files through VS, you need to ensure that:

1. Create and download the provisioning profile in VS.

2. In Solution Explorer, navigate to the iOS Bundle Signing tab and ensure that Scheme is set to Manual Provisioning, Signing identity is set to Distribution (Automatic), and Provisioning profile is set to Automatic:

In addition, you can try to generate an ipa file through the command line:

dotnet publish -f net8.0-ios -c Release

. For details, you can refer to Publish an iOS app using the command line.