There is no ebay.pt. Ebay seems to have put its clients from Portugal in the Spanish ebay, the problem arises that your call back option ceases to exist for Portugal as it is set for Spain only by default. 

You don't have an online help chat so we restricted to email. 

I get notifications on the item I want to purchase that it has a coupon. The price with the use of the coupon appears in green under the seller's price, under quantity you want to buy, there is another notice with the coupon's value, the coupon's code and the date it expires.

On the checkout window under Payment and Shipping there is also a notice, highlighted in yellow, to apply the coupon. If clicked, it gives the message: "It looks like the code isn't correct. Review it and try again." in red letters at the bottom left of the same window under the rectangle: add coupons. Adding the coupon there gives the same result and if the box is ticked I get the same message too. Please clarify if the coupon is exclusive to Spain just like the call back help service.