• Too big: the maximum file size is 50 MB. Compress it, or split it into parts.
• Blocked type: executable files (such as .exe and .bat) are blocked for safety. Zip documents instead of sending program files.
• Connection dropped: large uploads need a steady connection. Try again on a better network.
• No project selected (admin): choose a project in the Files page first.
• The Files app is off or hidden: check it's added in the App Library, and that the client's tag doesn't hide it.

There's no storage cap on any plan, so a failed upload isn't a quota problem. If it still fails, contact support with the file type and size.