You may see the message Disk Quota Exceeded if your account has a lot of files.
This issue is usually caused by exceeding your account's Inode Limit. In the sidebar of your control panel, you can see how much inode your account is using. This issue is most likely caused by your account reaching or approaching the 30,000 inode limit.
Every file and directory in Linux (and other Unix-like systems like MacOS) is an inode. When a system has too many inodes, reading and writing files takes longer, which makes webpages take longer to load. As a result, we have implemented a 30,000 file and directory restriction for free hosting accounts.
You will need to remove files and folders from your account to reduce your inode use. Check your account for scripts you no longer use, temporary files that may be removed, and other stuff that is not necessarily required to function your website.
The inode counter is not updated immediately when you delete anything from your account, so it might not go down straight away. The counter, on the other hand, should be updated in a few hours.
If your account has no data that can be removed and you require more inode space, you should upgrade your account. You will receive much greater inode limitations with a premium hosting account.