Hi Guy Hobbies,
Are you using Adobe Send, or uploading files to cloud.acrobat.com?
Please clear the browser cache, and then log in directly to https://cloud.acrobat.com/files. You should see a list of files that you've uploaded to your cloud.acrobat.com account. Click Sent Files to see a list of files you've sent via Adobe Send.
Please let us know how it goes.
Here are a few more things to try. . .
Try uploading the files as part of the Send instead of uploading them to your Acrobat.com account and then sending them. Note that these files will still show up in your Arobat.com account.
If a particular file is giving you problems, try renaming the file and trying to upload it again. That sometimes will resolve the issue.
Also check your internet connection. I could also be possible that the client dropped the connection during the upload. In this case uploading the file again should work but if not as I said earlier try renaming the file.