pdf download stopped working

Woocommerce version 2.5.5
Booster version 2.4.3
Booster plus 1.0.5

I have duplicated a fully working site to a test domain but on the test domain the pdf invoice is not working. The page refreshes to the same page
with this behind the url: /?order_id=694&invoice_type_id=invoice&get_invoice=1&save_pdf_invoice=1

How do I get the pdf’s to download?

Thanx Wendie

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