It's important to use the correct hand gesture when using your ring at a compatible contactless terminal.
In order for the terminal to get the best signal when it talks to your ring, you should use a 'knocking' gesture with your hand. Curl your fingers into a fist shape and approach the terminal as if you were going to knock on it.
Hold on your fist in this position over the terminal until you see confirmation of payment, or hear the confirmation beep.
Here's a quick visual guide on the correct hand gesture to use when making payments with the ring.