since Metalogix is a Microsoft Gold certified ISV partner, and we have a number of SharePoint products (e.g., SharePoint migration solutions and Selective Restore for SharePoint backups), we were invited to join the TAP for the hosted version of SharePoint, SharePoint Online. we were also a launch partner since our SharePoint Site Migration Manager software allows customers to copy/migrate SharePoint sites, lists, items, etc. to or from SharePoint online. SharePoint Online is also referred to as MOS, since it's part of the Microsoft Online Services offering.
anyway, we found that our users were having issues with their MOS passwords. I tried using the admin interface to reset the passwords, but it didn't seem to help. I haven't figured out what causes the original issue, but I do have some insight into why the reset isn't working.
if you try and reset a password twice through the regular user interface, you will see an error message saying that passwords can only be reset once a day. in the admin interface, there is no such error--it will just let you go through the process, but it simply won't work.
the workaround to this problem is to use the admin interface to disable the account and then re-activate it. doing this will reset the account and you'll be able to successfully reset the password.