Calls and Meetings with Invitees asking for User Name and Password login on IIS

We are using version 7.6.4 on IIS with Windows Basic Authentication for our installation.

If there is a meeting or call that has Invitees it will the Windows Log in will pop up asking for the user name and password.

We have SuiteCRM set up to use Active Directory on https.

I’ve tried adjusting the permissions for various parts of the Security Suite but the only thing that works is if I have everything set so that everyone can view / list which doesn’t work since we have several groups.

Any ideas on where the Invitee / Scheduling is checking for authorized users? Or why this would be happening?

Thanks,