I emailed eIS a few days ago because of a similar problem that many others are having, here's what they replied to me:
There are sometimes some more in-depth restrictions to specific markets within eIS, even among items that are broadly eligible for the program. This is not necessarily because those items can’t be shipped to that market, but because there are added regulatory barriers for a program the scale of eIS to support it.
This is particularly true for FDA- and CPSC-regulated items. While those items can be self-shipped fairly easily still, there are additional hurdles making it more difficult to get it across the border when using eIS.
We’ve started out with a more conservative approach to identifying those items that might be subject to these regulations. It is often based on subcategory but can include things like item specifics or title keywords. However, we are refining our criteria in the coming weeks to hopefully remove that US restriction on more items. While I can’t guarantee this will remove the US eIS restriction for all your listings, it should dramatically reduce the number of restricted listings. In the meantime, I might suggest adding a secondary self-ship option to the United States if you’d like to ensure that those items can ship to that destination.
In my case, most of my items are vintage and I'm guessing some materials (metals like brass and cast iron) are probably being blocked because eIS can't handle the customs documentation yet. Or something like that. I don't fully understand all the fees and issues associated with tariffs and duties, hopefully they figure something out in the next few weeks. My sales and views have been abysmal these past few months and my only listings that generate any interest are being blocked to US buyers to top it all off. I have a ton of new items I've been meaning to list but I'm scared that most of them won't be available to US buyers.
