Unable to Sign Xamarin.Mac App – "Warning: unable to build chain to self-signed root"

I am trying to sign a Xamarin.Mac application using my Developer ID Application certificate in Visual Studio on macOS. The app is successfully built, but when I attempt to sign it using codesign, I receive the following warning and error:

Warning: unable to build chain to self-signed root for signer "Developer ID Application: Team ID()"

<path-to-app>/SFSecure.app: errSecInternalComponent

What I have tried so far:

1. Verified that my Developer ID Application certificate appears correctly in Keychain Access under "My Certificates".
2. Ran security find-identity -v -p codesigning and confirmed my Developer ID is listed.
3. Ensured my login keychain is unlocked using

security unlock-keychain ~/Library/Keychains/login.keychain-db

4.Tried specifying the keychain explicitly using

security list-keychains -s ~/Library/Keychains/login.keychain-db

5.Checked for missing or expired WWDR (Worldwide Developer Relations) certificates and intermediate certificates in Keychain Access.

Despite these steps, the signing process still fails with the above error.

My Questions:

1. What does the "unable to build chain to self-signed root" warning mean in this context?
2. Is there an issue with the certificate trust chain, and how do I verify or fix it?
3. What are the intermediate certificate requirements, and how do I ensure they are properly installed?
4. Are there additional steps required for signing a Xamarin.Mac app correctly?

Any guidance on resolving this issue would be greatly appreciated.