Hi ​@cwalker  Welcome to the Box Community!

A few questions to help determine where the issue is coming from and assist in resolving it:

1. Are you or your co-worker uploading to your own Box accounts, or to someone else’s folder as collaborators?
2. If it’s to someone else’s folder, have you checked with the owner about their available space and upload limit? This is to ensure they have sufficient storage and room for new uploads.
3. Can you try clearing your cache and cookies before attempting the upload again?

We appreciate your patience and cooperation, and I look forward to resolving this matter. 

Thanks, ​@Jey Bueno Box 
We’re collaborators trying to upload to someone else’s folder that they created for us. We’re pretty new to this, having only been using it since November or December, but haven’t had any issues until now.

They have checked on their end and say there’s plenty of room. Oddly enough they can still upload files so they don’t know why we can’t.
I can still create folders and download from there, it’s just the upload that is failing. And while a file is in the process of trying to upload (sitting at 100% but still processing before saying it fails) if I try to open the file it will give a message saying it’s in use by the browser. 

I went through the troubleshooting tips that I could find, including updating my browser and clearing its cache and cookies, but still got the same result.
I even tried on a newly created VDI that had the latest version of edge installed but never used, and that didn’t help.

The issue was discovered, our firewall decryption and BOX weren’t getting along. A network engineer had to allow traffic going to BOX to bypass the decryption.