So if QMC Utilities works but you are unable to import and you are getting a 403 that is interesting. We had an issue with 400s on rules that had been deleted and an attempt was made to add the rule again with the same guid which we addressed in the latest build (2.0.0).
With a 403 it's likely certification because the sa_repository account is being used to import the rules.
At what point do you get the error? after uploading a rules file? Please open an issue on github here: Issues · eapowertools/QlikSenseQMCUtility · GitHub