It looks as if $DvSallowPromiscuous1 equals $null for a specific dvSwitch.
The Join function doesn't accept that.
Check how you populate that variable or build in a test where you first check for a $null value before calling the Join function
It looks as if $DvSallowPromiscuous1 equals $null for a specific dvSwitch.
The Join function doesn't accept that.
Check how you populate that variable or build in a test where you first check for a $null value before calling the Join function