Couple of WJ200 setting things important to remember.
If you are using a brand new drive - Do the power test and verify the Drive works.
Then when ready, connect up and change:
A001 to 03
A002 to 03
Verify all your settings for com speed (c071 to c078)
then once everything is set/stored/saved
POWER OFF YOUR WJ200, wait 5 min (I waited about 1 min and it was fine), Then POWER IT BACK ON (or reset it) - You need to do that before Modbus control will work
TX+ on RS485 adapter to SP on the Hitachi WJ200
TX- on RS485 adapter to SN on Hitachi WJ200
Verify your serial port settings on the PC, make sure they match the inverter, and set those in Mach as well.