I have a TS-451+ on the latest firmware (5.2.8.3332)
Every time I try to create a new user I get Failed to Create User
I have tried different admin level accounts and different browsers
Anybody knows what this could be? Stuck adding new users.
Note: Import from a .csv goes through the motions yet does not create new accounts either
Hi and welcome to the forum. 
Just checked here on a TS-251+ and a TS-216G - both running QTS 5.2.8.3332: no problems. User creation worked fine both from the original admin account, and a second account with admin privileges.
Is anything shown in the System Log?
On setups with new Firmware, the ‘admin’ account gets disabled, re-enable it and test again.
The log doesn’t have an entry showing any error. Even the multiuser create says it worked but no new users show up on the user list. Is there a way to test user creation using ssh just to see if it works?
Yes, use the QNAP nasutil binary for this:
user_add testuser testpassword1
… but its output is a little terse. Example: I requested it to create a user that already exists, which generated no error message (but did at-least produce a return code of 248).
Well, I was able to SSH and create a user and assign a password. The user did show up in the GUI user list.
I cannot log in as the user because it’s trying to force me to do a password change. And that Fails.
So, it feels like a GUI / permissions issue. I really dont want to factory reset this thing.
Probably a good time to create a support ticket with QNAP so they can assist.
Regarding this issue, please open a support ticket for us. Our Support Team will be able to assist you further! Thank you!