I checked your account, and it seems that you have reached the inode limit for your account. This means that your account contains too many files and directories, and you will not be able to create or upload new files or directories.
To fix this issue, you will need to reduce the number of files and directories on your account. For example by removing unneeded files. If you have multiple domains on your account, and fewer than three active accounts, you could move some websites to a separate account instead.