I'm aware of this, currently looking for advises on what settings to change!
The most common issue is the upload folder don’t having write permissions by ASP.NET user.
Common error is actually timeout because the connection is too slow or the file too big. You can see that uploading a small file actually works.
If now adjusted the setup, so you should be able to upload a bigger file and not experience timeout. Before the setup was 10MB and 1 minut. Now it's 50 MB and 60 minutes. And if you have a bigger file, then contact me again.