Symptom
When using a Kontrol MK3 keyboard on Logic Pro, the display shows a blank screen.
Cause
The input and Output ports in Logic's Control Surface Setup can sometimes be reset or reconfigured incorrectly.
This may happen when connecting multiple keyboards at the same time or one after the other.
Solution
In Logic, open the Control Surface Setup and set the ports back to KONTROL S49 MK3 DAW to resolve this issue.