If you are getting an error message, when you try upload an image via the Upload module in the product designer, this could have several reasons.
PHP Server Error
Your server throws an error and the upload is canceled. Please look into your PHP error log and check for any error. The log file will help you and tell you what was the problem. For any missing PHP function or any other server-related problems, please contact your provider, our support team can not assist with server configuration.
Firewall (WordFence, Sucuri)
Many firewalls like WordFence or Sucuri are blocking the request to this file:
This file handles the image upload and needs to be whitelisted in your Firewall settings.