Adding/Editing user account is not updated well

I purchased EX4100.
Soon after adding or editing user information, it pop ups message showing “now updating”,
and then I tried to login to shared folder with new account or modified account, but I can’t.
After rebooting WD4100, it seems to work with new account, but my question is Do I have to always reboot ex4100 for the change to take effect?
Doesn’t it take effect immediately as soon as it is updated?

It should take effect during the “now updating” dialogue screen. If you tried to login from a Windows PC, be aware that Windows is using cached credentials if you login to a UNC network folder. You can avoid this by using the IP-Address instead of the hostname for mapped network drives. This is a Windows specialty, valid since decades.