After a few days of comparing this app with the other one, part of the same bundle, that Archives without a problem, I finally found the problem: A second Fabric script ..that should be used for Answers which was giving me problems and I just put aside using for the moment. I forgot to delete the script for it.
Now that I think about the script could be well be the reason for Answersnot to be working ..time to investigate it ..
Well.. hopefully this will be of help to others..
The incriminated script:
"${PODS_ROOT}/Fabric/upload-symbols" -gsp "${PROJECT_DIR}/GoogleService-Info.plist" -p ios "${DWARF_DSYM_FOLDER_PATH}/${DWARF_DSYM_FILE_NAME}"