I was trying to buy it from my Sales page.
Here's a second issue. I listed another coin, exactly like the first one mentioned, but I changed the category thinking that would allow it to be insured. It did not work. Again, I tried to insure it from my Sales page and received the same "error" message, items from the silver eagle category cannot be insured. I changed the category specifically for this reason. If I would have know this was going to be an issue, I would have used USPS insurance. Once again, I'm out of luck.