Basically… using BTC on the DEX is a pain and requires the buyer to perform an additional BTCpay action once a BTC order is matched.
It looks like what happened is
1.) You listed some XCP for sale for BTC
2.) Your order matched with someone else who was looking to buy XCP with BTC
3.) The XCP buyer needed to make an additional BTCPay transaction to actually pay for the order
4.) The XCP buyer failed to make a BTCpay transaction
5.) You clicked the cancel button to cancel your order
Going forward, I would avoid using BTC on the DEX as most likely your going to continue to have issues like these with matched orders expiring, etc.