Travel booking sites must comply with Copa Airlines cancellation policy in order to sell tickets on the airline's behalf. If you book travel on one of these sites and then need to change or cancel it, you may be charged these fees to the airline. Also, usually, they don't offer refunds. The maximum value that can be obtained is a voucher for the value of the ticket to be used at a later date, usually specifying that the voucher must be used within one year of the original travel date.
This isn't necessarily a bad thing, but keep in mind that travel booking sites may cost you a little more than the original ticket, since trying to use the coupon can deduct the exchange rate. Be aware of tour booking sites, they can offer discounted prices based on quantity, so cancellation policies are very strict.