Gwp's can be very hard headed. I've had 4 over the years. Go back to the start, in a place with low distractions make him sit and stay right beside you. Don't praise him, then use a release command to let him move. It might be "off you go" or similar. Just do that for a few times.
Then make him sit and take a step away wait 2-3 seconds then step back, wait 2-3 seconds and give the release command. Slowly build up the time and distance before releasing. Don't take him back out in the bush until you have it sorted.
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