I had the same problem. I needed to manually add the IP addresses in (they were greyed out) to the ghosted values before it let me hit save. That seemed to work, but then I found a ton of websites that wouldn’t resolve – even basic ones like duckduckgo.com and sony.com. I also couldn’t even reach the Amazon app store. I’m not sure if the connections were temporarily or permanently unavailable, but I’ve since reset things back to the way they were. 🙁 Just not working correctly.
Just tried changing the first IP address to .20, but the problem is still there. Exact message from the Silk browser when trying to go to sony.com: