Zapier error (Asana to Buffer image attachments)

Hello,

New here!

I am trying to setup a Zapier interface for Asana and Buffer- scheduling a social media post from Asana via Buffer specifically.
Everything works, except the most important part : the image attachment.

It returns an error “The provided image does not appear to be valid.”

How can we allow Buffer to retrieve an attachment from Asana - has anyone achieved this? The Zapier forum hasn’t been very helpful so far.