hi i found the answer – i have 26 printful products on my woocommerce (no other products, its a printful only setup currently)
I had on my woocommerce turned two of the products to “draft” as I didnt want them on sale. This disrupted the entire thing ands hipping prices werent syncing for any products thereafter. as soon as I turned those products back to published within woocommerce, it all resolved.
Not sure if thats a bug or expected!