As has been explained in numerous other threads on this site, using BTC on the DEX is a bit more of a complex process than using ANY other asset on the exchange due to the fact that BTC can not be escrowed by the protocol.
1.) You have to place an order to buy or sell an asset for BTC
2.) Your order has to match with someone
3.) Once your order matches with someone, the person paying with BTC has 20 blocks to send a BTC payment or else the order match expires.
What is happening is that your order to buy XCP for BTC is matching with other users, however you are NOT sending the BTC payment within 20 blocks, so your order match is expiring… you can verify that at this url https://xchain.io/tx/1452523
If you were to use a wallet like freewallet.io desktop wallet, the BTCpay transaction would automatically take place when your order was matched with someone. We disabled the BTCpay functionality in counterwallet.io a few years ago because it is HIGHLY insecure to leave a browser/wallet window open in order to detect order matches and send the BTCpay transaction… anyone who walked by your computer would have full access to your funds, which is why this feature was disabled in counterwallet.
We also are getting ready to release a new feature called “Dispensers” which will allow you to buy any asset (including XCP) from a dispenser by just sending a BTCpayment to the address… so, within a couple weeks you will be able to just send a BTC payment and get a token (or many tokens) sent back to your address without having to do BTC trading on the DEX (which as you have noticed, requires an extra step of sending a BTCpay payment).
For all other assets (over 75,000+) besides BTC, the Decentralized EXchange (DEX) works exactly like traditional exchanges where orders are placed and executed immediately when orders match with one another.
TL;DR… try using freewallet.io desktop and buying the “FULLACCESS” token so that you will have full access to the DEX and be able to use BTC on the DEX just like every other asset.