Hello @Regan.D,
I can't help but wonder if the issue is the long concatenated URL is the issue. The docs linked to don't use that format. I would use the format given in the 'Example Body':
{
"status": null,
"description": null,
"virtualNetworkName": null,
"ipPoolName": null,
"authenticationPolicyName": null,
"trafficType": null,
"scalableGroupName": null,
"isL2FloodingEnabled": null,
"isThisCriticalPool": null
}
Best regards,
Alex