Help with Select Expression

[Jaros]

I have a table called Line items where I record the individual items of an invoice from a supplier.

I then have an additional table, called [Daily Invoices]where I want to save the total and take a photo of the invoice for saving.

In my total table I put the following expression

SUM(SELECT
(Line Items[Cost],
Line Items[Invoice No]=Daily Invoices[Invoice No]))

I get the ok from the expression assistant but nothing happens when I open up the Daily invoice Table and input the Invoice number of the line items I just added in.

Is there something wrong with this expression?