ASUS RT-AC56U..... now unable to connect to Internet

[#1]

Hi everyone.  I've just got an ASUS RT-AC56U router, but it will not connect to Internet.
I followed the set up wizard using the following....
PPPoE
Enabled wan
Enabled Nat
Enabled UPNP
Connect WAN DNS Auto
MTU 1492
MRU 1492
The network map says there's an internet connection, but I get a BT webpage saying wrong/unauthorised settings.
I'm also using the BT Openreach modem.
Anyone got any ideas, please

[#2]

Do you have a VLAN ID option in the PPP settings? If so, set it to 101.

[#3]

Thanks, but I'm new to this.  Not sure where that would be.  I've looked at all the settings, but can't find any mention of VLAN or PPP.

[#4]

You don't need to worry about VLAN settings as the BT modem sorts that out for you.
Double check that you've entered your Plusnet username and password in the PPPoE setup stage correctly.  If this is definitely correct it may be that PN haven't enabled your account yet.

[#5]

I've checked all that.  We've been with PlusNet over a year now and everything works with their router.
This is what pops up on web page...
You have been connected to this page due to one of the following reasons. You must now shut down your internet browser and internet applications before attempting to reconnect. This may clear the issue immediately, if not then please select the appropriate action from list below.
• Your service provider is currently unable to accept your connection request, please wait and reattempt later or contact your service provider for more information.
Or
• You have attempted to access an invalid Service Provider domain, check your user details.
Or
• You are testing your connection using bt_test_user@startup_domain. Please proceed to next step as advised by your Service Provider
Or
• You are testing your connection to your service provider using bt_test_user@domain. where "domain" is your Service Provider domain name. Please proceed to next step as advised by your Service Provider.
Or
• The access circuit to your Service Provider is currently down. Your service should be resumed soon. Please try again later or contact your Service Provider
I thought I would be connected by following the Quick Internet Set Up and then it would be just setting parental controls etc.  I must be missing something.

[#6]

OK. All is well with your account if the old router works fine.
Check, check and check again your username, especially the plusdsl after the @

[#7]

Ah missed that the Openreach modem was still in use. Possible stuck session. Power off the modem and router for a short while, power up the modem, give it a couple of minutes then power up the router.
If that doesn't work then let me know and I'll jump onto the VPN and see if I can work out what's going on.

[#8]

Ahhh.  My PN paperwork says the username is my account name and not my broadband username.  So there's no plusdsl.net on the end.  I'll try that. Thanks

[#9]

Give that man a cigar

[#10]

Thanks guys. All sorted..... I turned everything off and waited and then on again (Thanks Bob).  I also changed username (added plusdsl.net) and it all works.  So not sure which bit fixed it, but it all works now.
Thanks again

[#11]

and thanks to pwatson as well