I have narrowed it down. Removing the Primary Key from the table vol_space and allowing NULLS on the server_name field inserts records but without a server name. Somewhere the server\computer name is not being populated, maybe in the Out-DataTable funtion. The column names picked and added to the data table are:

FreeGb

Label

Name

PercentFree

SizeGB

SystemName ?

UsageDT

SystemName appears to be the culprit?