If it’s working from Postman but not from Mendix I would suggest turning the Log Level of the REST Consume node to TRACE. This will log all headers and body of the request and the response from the server. You should then be able to compare this to what Postman is using. You may find a difference in the request headers that you need to replicate in your Mendix application.
Hope this helps, good luck!
hii Nathanael Hazard,
your issue is related to the connection not file size , i think your server not recognizing the connection with you.
for more info refer this link below.