Why did I get API error code 10548?

[princebruno]

I am probably not the first one or the last one asking this question.

Paypal support is not responding to this question so I though i'd post here.

Using gravity forms paypal pro and have a paypal business account. all the lights are green so communication exists.

By the way i set may gf paypal pro set to sendbox.

followed already a few troubleshooting steps but no luck

Anyone had a similar issue and can help figure out what i am doing wrong?

Thanks