Hi @samb, indeed you are correct that a special licence file is required in conjunction with the Tobii 4C tracker to allow proper operation the Pro SDK.
If you could kindly confirm if you already have this licence and are thus experiencing issues in correct implementation, we would be pleased to try and help you out however please bear in mind this forum is principally intended to support the Tobii Core SDK and associated hardware as the Tobii Pro SDK has it’s own dedicated support staff courtesy of the Tobii Pro business department. Many thanks.