I have recently installed OS Services Booking and are using the PayPal_pro module to take payments. Our purchase testing crashes with this same error 'Security header not valid'. We contacted the OS Services Booking support team and all they have told us to do is check the API Credentials. I checed the fourm and all I could find was to Creat Recurring Payment Profile, and use the new API
the error is still there. can you Help me please???
