If you're trying to upload the attachment to your project, and you keep getting an error message, it's most likely due to the unsupported file type or the file size is too big (max 10MB). In this case, we can offer two possible solutions:
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 1. Send an e-mail with the attachment to [email protected], and we'll add your attachment to the project
 2. Upload your attachment to Google drive or any other file hosting service and simply add the link to your project (please make sure the content is visible to anybody with a link).