It unclear to me whether it is a Pinterest or Zazzle technical issue.
Since two or maybe three days, I noticed, it is impossible to add a product tag to a Pinterest pin. It results in an error (Invalid parameters).
Today I tried to pin by using a collection link it returned the “406 Response Code” (also the reason I assume it is a Zazzle issue).
Loading an image to Pinterest and adding a Zazzle link works.
Sharing a collection or product works too.
Found your posting because I just experience the same problem getting the “Invalid Parameter” message when creating a manual pin and trying to link to a product.
But it only happens when trying to link to a newer product (created within the last two days) and works fine for older products. Maybe it is a product catalogue issue on Pinterest’s side?
Wait a while. It was corrected last time. Seems it occurs every now and then.
I had the same problem yesterday when I added a product tag to a pin and used a link for that.