My Nintendo Can't Claim Physical Rewards / Can't Add Items to Cart / Merged Shopping Cart Error

Just wondering if anyone could suggest any info to fix this issue with My Nintendo not adding rewards to cart.

I am logged in on My Nintendo trying to order physical rewards. When I click "add to cart" it never gets added to my cart. When I click on my cart I see nothing in it, but I get a message above. I get the message, "While you were logging in, we found (1) items in your shopping cart. Don't worry, we brought them with you and merged them with your previously saved shopping cart."

I don't see a way I can remove the item that it believes is in my cart. I believe this might be the reason I am not able to add anything to my cart. I found one other similar post to this, their item was to change your accounts language to English. My account is already set to English, and switching back and forth didn't help. I'm wondering if could force empty my cart to remove the invisible item. I've tried on multiple devices and browsers. Thank you!