/scripts/fixquotas --force
It may give errors like the following, if the problem is not solved completely.
Resetting quota for abcde to 500 M edquota: Quota write failed (id 32230): Invalid argument Resetting quota for xyz to 500 M edquota: Quota write failed (id 32010): Invalid argument
In that case, a quick reboot of the server will help to solve the problem. You may restart the server via SSH using the command
shutdown -r now