One tool our instructors use to create a class.lst to populate a WeBWorK course may omit a leading zero from a student ID (= initial password).
It appears neither old nor new classlist editor (used subsequently by an instructor in a web-browser) can fix that, but an administrator with shell access can use the webwork2/bin/newpassword tool to do the deed.
This is, almost certainly, an issue distinguishing a number from a string. On the other hand, quoting a "0#####" value in a class list editor was not a fix (but may have created a subsequent difficulty when such an editor failed to create a usable password which did not begin with "0"). SIGH --- first week of classes seems to generate "new" difficulties each semester --- back to "normal" next week (I hope).