I ran into the same error when trying to upload my Unity app.
This is what fixed it for me:
Go back into Unity > Edit > Project Settings
Player tab > Other Settings
Check "Override Default Bundle Identifier"
Enter your bundle identifier (for me I was updating my app that exists already on the app store so the one in my Unity build didn't match the one on the app store)
Enter your version and build number
Enter your Signing Team ID (you find your Team ID at developer.apple.com > Account > Membership Details > Team ID)
Check automatically sign
Re-build and open in Xcode
Once I did that I no longer got this particular error message, but got a framework error and had to delete my Unity Framework extension which I found out how to do here.
After that, the build and upload was successful. Hope that helps, my fellow iOS devs.