Ah! Looking more closely you are using filter and search, you only have to use Search like this
SortByColumns(
Search(
TextSearchBox1.Text,
"Address"
),
"Address",SortOrder
).
If you want to use StartsWith change the search section to:
Filter(
'SGN SLG Master List';
StartsWith(
Address;
TextSearchBox1.Text
)
)
By the way, as you see I dont use @[] when refering to a datasource.
Please note StartsWith is delegable, Search is not.