The PPF files opened on the press computer can show in negative rather than positive.
Symptoms
User on the press receives PPF files that are in negative. So, it is not possible to use them to control the press keys.
Solution
The cause of the problem could be the Output Format of the PPF file. Using ASCII 85 can give wrong result on the press. The plate would appear as exposed in negative mode.
To get the correct result, use ASCII Hex as Output Format in the Nexus workflow.