Attachment file does not exist error

See https://contactform7.com/configuration-errors/file-not-found/

I have tried both absolute and relative URLs. Most recently I used:
uploads/2017/09/The-Rates-Card.pdf
which should attach the following PDF:
https://www.farmerdirect.com.au/wp-content/uploads/2017/09/The-Rates-Card.pdf
however the email is not sent and when I check the Postman SMTP Email Log I see the following: Unable to open The-Rates-Card.pdf for reading

I’ve tested this further by adding a second form to my site with a single mail configuration. The message is sent fine when there is no file attachment, but fails to send when there is a file attachment. As stated in my previous post I have tried both relative and absolute URLs.

When I attempt to use absolute URL for the file attachment as either:

https://www.farmerdirect.com.au/wp-content/uploads/2017/09/TEST.pdf

or

/wp-content/uploads/2017/09/TEST.pdf

I get the config error “Attachment file does not exist” appearing beneath the File Attachments textarea

When I attempt to use the absolute URL:

/home/farmerdd8fuued/public_html/wp-content/uploads/2017/09/TEST.pdf

or I use the relative URL:

uploads/2017/09/TEST.pdf

the File Attachments textarea validates but the message is not sent upon submitting the form.