As I understand it, HighZ digital disconnects outputs. So if You have pin configured as output You neither read notr write.
I had the pin configured as input and output. After outing the signal the mode is switched to HiZ so that I can read it. It does switch and the voltage at the output starts to drop but I cant read the pin after that. For now I am using two pins as a work around but it would be nice to get it on one pin.
You have to check if the proper registers have been set after issuing command.
You must trace in- to output command (DriveMode).
Another possibility is to use bidirectional pin bufoe