There could be a number of reasons why your transaction isn’t showing in your activity list:
The merchant might not accept cards issued in a different country. This is often the case in the US, where many businesses only accept US cards.
If it was an online payment, there might have been a technical issue with the merchant. Try deleting your card details from their website, troubleshooting your browser and making the payment again.
The shop or business you bought from never asked Wise to authorise the payment.
If your payment was accepted, the terminal where you used your card might have been offline. This usually happens on an airplane or underground. If you spend more money than you have on your balance before the merchant captures this transaction, your balance might go negative. When it happens, you need to top up your balance to keep using Wise.