DPS Signing Tool Error - Missing Team ID Prefix

[#1]

Im using the new DPS signing tool for the first time and I continue to receive the error message:

"Error Signing the App: Missing the team identifier prefix"

Any guidance would be greeting appreciated.

[#2]

The App ID's prefix used in the certificate needs to match the one you have in your mobile provisioning profile, maybe they are different, see if that helps: Technical Q&A QA1879: Resolving App ID Prefix Mismatching

If unsure, just generate a new App ID and go through the process in the Apple developer portal again to make sure you have the correct certificates and provisioning profiles on your machine.