I have been using Confluence for many years and have always been able to upload images onto pages. However, a couple of weeks ago I started getting errors when trying to do this.
Dragging an image file onto the page results in a Failed to upload error...

If I go into the attachments of the page I am not able to drag a file to attach it...

However, if I try through the Attach Files ->Choose File part of the attachments page then it does work. But then I've got no way of displaying that attached image on the page.

The issue happens in Chrome, Firefox and Edge browsers. I've logged out and back in again to Confluence, have cleared all cookies etc, but still have the same issue.
Some other colleagues have tested it and don't have this issue.
We also use Jira, and I am able to add attachments there.
Has anyone experienced the same problem before?