Stuck on first time login

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I installed Cacti 0.8.8 base on following instruction on my QNAP TS-453A NAS.
https://forum.qnap.com/viewtopic.php?t=127577

But I stuck on first time login using admin/admin. If I type admin/admin right, it will just like nothing happen.

https://imgur.com/a/4CRFj

And cacti.log will indicate as following:

2017-10-05 21:10:49 - AUTH LOGIN: User 'admin' Authenticated

But if I type anything else, will show:

"Invalid User Name/Password Please Retype"

My NAS already got build-in web server. But this Cacti QKPG has dependency Qapache. So I install Qapache and make sure php.ini don't mess up each other.

phpinfo of Qapache for Cacti
https://imgur.com/shdkQZu

phpinfo of NAS build-in
https://imgur.com/6HqeiMk

Any idea or suggest will be much appreciate. Thank you!