This error has been bugging me for over a year now:
touch: cannot touch `/aquota.user': Permission denied

This generally occurs when performing any function where the quota system is being modified, such as changing an account’s quota, suspending/unsuspended an account, or running one of cPanel’s quota scripts. First, check the permissions of /aquota.user (or the actual quota file being referenced in the error):

lsattr /aquota.user

It should ideally return this output:

------------- /aquota.user

If you see an ‘i’ in there though, it means that for some reason the quota file has been made immutable, and therefore cannot be modified by the system. You can remove the immutable flag by running:

chattr -ia /aquota.user

That should correct the problem, and allow you to proceed with the account function you were trying to perform.