Can NOT upload anything

Check under Tools > Site Health to see if any messages are displayed there. My guess would be that WordPress cannot save either because of incorrect access rights or because of insufficient free storage space. Both should be visible there as messages.

What message do you receive when you upload a file, for example? Feel free to show us a screenshot of it, see: https://wordpress.org/support/forum-user-guide/block-editor/#adding-screenshots

“Could not copy file” indicates that files could not be saved in the hosting. This can be caused by a lack of free storage space, incorrect access permissions, or incorrect configurations in the hosting. I would recommend that you contact your host’s support team for clarification.