Account deactivated and money withheld…

So I had been selling on Amazon for 7/8 years.

Brand registered, 100% health on everyone and selling FBM & FBA.

I had 3 of these to sell about 3 years ago and found the item already on Amazon so I used the Asin.

ASIN: B089QNK4YB

I then get an email 6 months ago now stating my account has been deactivated due to this item.

After lots of back and forth they said this type of item is not allowed.

I had an online video call with disbursements to show suppliers etc but they point blank refused to pay the £1400 they are holding from me..

Is this normal practice and is there anyway of getting my money back ?