Azure - "VMScaleSetCannotReferenceLoadbalancerWhenLargeScaleIsEnabled"
'VM scale set cannot reference a load balancer when LargeScale property is enabled.'
The error may well leave you as puzzled as I was!
There is a checklist of things you require
/en-us/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-placement-groups
STANDARD not BASIC for the Load-Balancer is the first thing to check..
/en-us/azure/virtual-network/virtual-network-ip-addresses-overview-arm
and you probably need a Standard SKU for your Public IP too.