Shopify Payments, Stripe, PayPal, eBay, Amazon, and other payment providers and processors have restrictions on what products can be sold through them.
Limitations include: drug paraphernalia, substances designed to mimic illegal drugs, high risk businesses, pharmaceuticals or pseudo pharmaceuticals.
For the complete Shopify Payment limitations you can browse section B(5) of their ToS.
Two Tap also flags products from certain brands that Two Tap does not have a direct relationship with. For instance, if one of our suppliers sell Microsoft products, but Two Tap has no clear relationship with Microsoft, that product will be marked as restricted. Two Tap is working with brands on dropping the number of restrictions continuously.
If you try to sell these restricted product with the mainstream payment processors your accounts might be disabled, frozen, or banned.
You can still sell restricted products if you work high risk payment processors. There are companies like eMerchant Brokers designed to help you out. They also have very easy to set up integrations in the platforms.