Thank you! 
And to double check, do you know if you're using the new file button or the older one? We can confirm via a screenshot of the right panel to show the file button properties (the newer button has a different set of customizable properties), or even better, your left panel, expanded out to show the data structure of your file button.
Do you know what file structure your resource is expecting from the Attachment field? General API file types expect the below format:
{
name:
size:
lastModified:
type:
data:
}
and you can make that happen by placing {{ {...fileButton1.files[0], "data": fileButton1.value[0] } }} directly in the field!
