Coinpayments is for hosted wallet solutions and general payment gateway for cryptocurrency ("buy now" buttons, shopping carts, and things like that). They aren't an actual payment processor like Bitpay. They can't convert coins to fiat, so it's not a merchant alternative for Bitpay. But as a consumer, I'd like to see them succeed.
Bitpay's problem is that it is bitcoin only and they never imagined that the mempool backlogs could get so big and thus didn't have processes in place to deal with that.
Hopefully Bitpay will see the light and enable alts.
Actually, Bitpay has bigger problems. Regardless of transaction backlogs, they are often not marking invoices with
confirmed transactions as paid, leading to problems like the OP's.
Regarding alts, Bitpay announced a month or two ago that they are working to add multiple. The first is Bcash. I'm guessing they will also be adding ETH and maybe others too.