I am having exactly the same problem. I was on the phone to a paypal engineer and was given a load of information that was wrong. I f you create an image 200 px wide by 75px high and less than 100kb and upload it you just get the red x box. I have tried uploading the logo directly. Hosting it on imageshack and even hosting it on my own server and it still wont work. I am begining to think there is a fault with your invoice template page as there is no other option left to try. A very disapointed and frustrated Paypal customer 😞
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