Often this error message appears when uploading images to an item listing or into your storefront.

We recommend individual images to be below 2mb in file size (the smaller the better).
When uploading more than one image at a time it is important that the sum of all of your images does not add up to be greater than 10mb in size.
This will ensure your images can be uploaded and processed by our web server.

There is a bunch of information in our help on images as well as other things.

Please feel free to contact madeit support if you have any questions.