Welcome to this forum John.
Maybe the firewall is blocking AC from accessing some component that it requires - many of them tend to be over-zealous. You may need to go into the advanced settings and giving it the necessary permissions? If all else fails, do you have the option to use a different firewall?
It would be helpful for us (and yourself) if you add your OS and AC details in your signature. You can create that by clicking on the profile button at the top of this page and filling in the details.