there has been an update from Apple in that space. After the update they do not trust self signed certificates anymore. Looks like that this is your issue. Try to allow http access to your Hub and QMC by changing this in your Proxy settings in the QMC:
I expect that to work. If you want to use https then again, an option would be to change the certificate into a trusted one if you have access to a CA in your environment.
I hope this is helpful.