I am trying to add a product but can not

Hi there… I am new to Amazon and trying to sell Knee Supports on this platform but every time I start filling up form to add a product my EAN number does not go through. I keep getting message that EAN does not match the product that I am listing. I purchased my barcodes with GS1 to avoid this issue but still no joy. On top Amazon support is good for nothing. They said my product ID is valid but there could be matching error where product information partially matches on an existing ASIN so i need to make required changes. So basically I need to change product information which is matching to ASIN identified by Amazon. So How do I know which areas need changing. I am really stuck here, I hope someone can help me with this issue…Thanks