All I had to do was move the "Key" value above the if statement.
for (var i = 0; i < sortedKeysArray.length; i++) {
var key = 'Tgt-' + sortedKeysArray[i];
if (!(sortedKeysArray[i] == "LineNumber" || sortedKeysArray[i] == "AttributeName" || sortedKeysArray[i].includes("Tgt-") == true ))
$scope.gridOptionsVatMakeRpt.columnDefs.push({
name: sortedKeysArray[i],
field: sortedKeysArray[i],
width: '20%',
visible: true,
cellTooltip: function (row, col) {
var value = row.entity[key];
if (value != null) {
return value;
} else {
return "No Value";
}
}