Hi,
Ive had this problem before and was able to talk with someone on the phone who was able to help. Now I can’t seem to find a phone number for shopify help line. Please help. I have someone who says " items in cart can not be shipped".
My guess is that there might be something missing in your shipping set up. Try taking a look that you have a working shipping rate for the address and that the products you are trying to test out in your cart are in the general shipping rate (rather than being in a custom shipping rate).
To look at your setup go to:
Settings > Shipping and delivery
Shipping
General shipping rates
General —> click the word manage
In here, check that you have a rate that would apply to the products. I hope it helps.