There is a Contact Seller button on every listing.
Some sellers were defaulted into the Global Shipping Program and have no idea that they ship internationally. Although eBay stopped defaulting new sellers over a year ago, US sellers get few enough international buyers that this may well be your seller's first.
So, try the Contact Seller button. If the button doesn't work, then the seller doesn't in fact want international sales and is unaware that he is telling buyers that he will accept them. And if the button does not work, there is no way of letting him know.
The GSP is a badly designed, badly implemented, and badly run program. And I spend a lot of time telling unhappy buyers that it is not in fact a cash grab or a scam.
If the Contact Seller button works, you may be able to work with the seller to correct the problem. Start by asking if she knows she is enrolled in the Global Shipping Program and if she can help you bid.
BTW, if you have no active Paypal account or if you have Unpaid Item Strikes, the block may be specific to you and unrelated to your location.