I downloaded the product manager version 1.1.6,ran the installer, immediately received the "No Internet connection warning"
* Checked hosts file for any entries referencing IK Multimedia (none found)
C:\Windows\System32\drivers\etc
* Momentarily Dropped VPN (Norton)
* Paused Firewall (Norton)
* Ran the installer again as an "Administrator"
Installer worked, no banner appeared. Did notice that it was installing version 1.1.7. When installer finished, the logon screen immediately appeared. Logged on and I was able to register my product and access the installers
Doing those items helped me run the installer and download the products. I also noticed that when I came back later to install other purchased products , the installer from within the product manager did not work until I paused my Firewall. I'll eventually look for what application process needs to go out so i can create an exception rule on my firewall.
I did reach out to IK Multimedia support the night before, I was worried that they wouldn't respond in a timely manner but they responded the next day but I had already figured out the issue. IK support response is good so hopefully you experience the same quickness
Hope this helps for users having similar issues
I'm also running Windows 11 Pro 23H2 bld 22631.4460