I am having the same problem, though I’ve updated the plug-in and have sandbox turned off. I’m about to try a different system unless this gets solved. Users get to payment, PayPal charges the event fee, but the EventPrime system shows the transaction as “failed.” People then try to register again and get charged multiple times by PayPal but failed on EventPrime. I know I’m using the free level, but I’d never pay for this if this is how things work!
