Apple Pay Not Working

Over several attempts on multiple days, Apple Pay is not working when purchasing on a site via Safari on my iMac and then verifying payment with the iPhone by double clicking on the side button. I keep getting a red exclamation point that the payment did not process and asking me to try again. I have enabled payment off the iMac in Safari preferences so that is not the issue and my Apple ID is the same across iPhone and iMac. Is there a way to fix this problem?