If the buyer too is slow or non-responsive. The escrow is automatically cancelled unless the buyer presses Mark payment done within the payment window (usually 30 minutes). If this was a mistake, you can reopen the escrow to finish the trade with this buyer.
Dispute the trade if there are any disagreements in the trade, you can open a dispute. After a dispute has been started, you can still release the Bitcoin and finish the trade (e.g. in the case a payment was taking longer than usual to arrive and a dispute was opened prematurely).
Not replying to trade offers can give you negative feedback. Turn off your advertisements when you're not trading. Tip: use the opening hours feature to automatically turn on and off your ads as you are available.