unable to check in: CLEARANCE FOR "NOT OK TO BOARD" TO city

unable to check in: CLEARANCE FOR "NOT OK TO BOARD" TO city

Advise the customer to communicate with below:

As shown on the reply this is an APP rejection by the ZA or UK or AE immigrations. Please continue to request for clearance the way you did before the ADC implementation. 

FYI:

The project implemented for APP (current APP nations ) are Dubai , London and  South Africa has APP implemented.