nahh..my pc gaming and sometime dl.
the real heavy downloader is my mom and dad..one youtube one dl drama and watch..
haha..

Stock after flash should be:

USR : admin
PWD : <blank>

or

USR : admin
PWD : admin

Different models but both stock (factory reset condition), probably yes different passwords
Same models both stock, should be same password.

Not sure how you set up the connection between the 2 of them so the safest way to enter the one you want to configure is direct lan cable connection to the router.

192.168.1.1 should be the address. If not try 192.168.0.1..

Not so sure, i dont have this router.

You can try finding

Wireless > Wireless Security
Interface > WLAN > Security
Advance > Wireless > Security
Something like that...

Make sure you can access internet from this router thru your current lan cable first ya, of cos it has to be connected to the 1st router that is connected to modem. Otherwise wireless wont have internet either...

Explain with more details what you are trying to do with your setup, if it's confusing for you it wont be clearer to anyone here.
Also, the wireless security password is for wifi only you cant log-in to router configuration page with that password.

Since you are using 2 routers, i can only guess that:

1. You reset wifi password and think it's the password for the router configuration, it's not. It's still the (admin ; admin)

2. If you are broadcasting wifi from both routers for roaming (auto switch to strongest signal), you need the same SSID & password for both, for it to work.
3. If you are broadcasting wifi from both routers without roaming (manually connect when you want to switch), you need to have 2 different SSID & password for both

4. If you are broadcasting 1 wifi only, from the 841... What do you mean by not able to use password? Cannot connect to it? You sure you trying to connect to the correct one? What device you using? Did you configure the wireless to support BGN modes?

Yep, the router wireless config on both must be indentical

Same type (Mixed-B/G/N on both / Mixed-NG on both / N-only on both routers etc..)
Same SSID (wireless name)
Same Encryption (WPA2-PSK AES Cipher)
Same Password
Different Channels on each (same channes can cause interference/packet collision)

Sometimes if the connection is unstable or not working, it's better to configure static IP on 2nd router & disable DHCP for less conflict

This is a good simple guide:
http://smallbusiness.chron.com/setting-up-...ssid-68675.html

Yep, the router wireless config on both must be indentical

Same type (Mixed-B/G/N on both / Mixed-NG on both / N-only on both routers etc..)
Same SSID (wireless name)
Same Encryption (WPA2-PSK AES Cipher)
Same Password
Different Channels on each (same channes can cause interference/packet collision)

Sometimes if the connection is unstable or not working, it's better to configure static IP on 2nd router & disable DHCP for less conflict

This is a good simple guide:
http://smallbusiness.chron.com/setting-up-...ssid-68675.html

Just to check:

1) Did you connect from LAN1 on the ONU to the WAN/Internet port of 841ND?

2) Did you select UNIFI MODE in the WAN connection settings?

Try this: in the WAN settings, after you entered username & password (Username: <your_unifi_username>@unfi and Password: ******) (I hope you entered the correct one) and saved it, click the "Advanced" button, then on the PPPoE Advanced Settings page, enter 30 for Detect Online Interval, then save it... see if it works.

May I know, what is it actually that you cannot connect? Any error message shown? How about IPTV service? Does it work?

Also take note Port 1 is for IPTV, so you must not connect any PC or laptop to that port on the router.

May I know the 2 grey cables, what are they connected to? Does the grey cable with yellow head connects to IPTV?

If all else fails, there are likely 2 possibilities left:

1) There is some configuration error, possibly wrong username/password?

2) You have a faulty device, get replacement under warranty perhaps.

Looks like it's possibly faulty unit.

I am currently using TP-Link TL-WR4300. Prior to that I actually used TL-WR841ND. Configuration for WAN is similar for both routers! I have no problems with both models.

Can you snapshot the entire Status page of the router settings?

If you cannot log in, means you have not configured it, hence your UniFi does NOT work!

Use your web browser and try go to either http://192.168.0.1 OR http://192.168.1.1, one of them should work! The username & password should be "admin" without the quotes.

One thing I am curious is, is this 841ND you have a brand new you bought recently? Or an old model that has been around for years? Because these routers have various Hardware version, the one that confirm working with UniFi is the Hardware V7.x & V8.x. Can you also look at the bottom of the router, there is a label with the version & serial number? If not sure, share us here a picture of it.

This should work. IP address & default username & password are printed there as well. But you cannot get in 192.168.1.1 at all?

Your connection is correct. But can you check if your network adapter (on PC or laptop) connected to the router has an IP address? Is it in the 192.168.1.x range? What is the Default Gateway?

Open your Command Prompt, type ipconfig then Press Enter.

In the output, look for the one under something called "Ethernet adapter". What is listed for IPv4 address, subnet mask & default gateway?