Paypal Error

Hi folks! I’m getting following error trying to pay via paypal:
Express check out API call failed.

Error code:
10002

Error severity code:
Error

Detailed error message:
Security header is not valid.

Short error message:
Security error.

It’s very important to me to set this right, my customer is already angry about this.

Also, i can’t get support credentials. My plugin doesn’t have the activation option. Maybe i have a older version?!

And, at last, i’ve translated the whole plugin to Brazilian Portuguese. Please be my guest to use my translation in your version, without charges.

https://ww.wp.xz.cn/plugins/booking-system/