Logo not showing on invoice

Hi Bas

I have had an issue lately with a new website that I am using your invoice plugin on, no matter what I do I cannot get the logo to display on the invoice. I have tried updating to latest version of the plugin and even copying the plugin from other sites I know it works on. its got me buggered.. any ideas? It just displays a red x in place of the logo. I have tried different file types, sizes etc and nothing works.

Link to invoice header screen shot > Link

https://www.ads-software.com/plugins/woocommerce-pdf-invoices/