Asus DSL-AC68U

[#1]

AshPowell    my speed is max  74down 17 up so nowt to be gained , also i believe i have the wrong type of cab for G - INP  to be used  

ooops just spotted my error

[#2]

Fair enough! I thought both would have it by now its been an age! As you say not like you need it anyway, gave me a good 5Mb (from 45 to 50) so more benefit for me.

[#3]

Please help... I'm starting to lose the plot here! 
I'm having a similar issue to OP by the look of it, Asus DSL-AC68U arrived last week and since then I've managed a stable connection with it just once.
When I turn the router on the adsl light just flashes (about 10 times) before deciding it can't establish a connection and stopping altogether, After another 30 seconds or so the process starts again.
However yesterday there was a breakthrough and all of a sudden the adsl light became solid and was able to connect to the internet... unfortunately it has since disconnected itself and we're now back to square one!
Going through the logs as the router attempts to connect I can see the following:
Aug  1 00:23:05 pppd[1095]: pppd 2.4.7 started by admin, uid 0
Aug  1 00:23:18 zcip client: configured 169.254.100.191
Aug  1 00:23:18 hour monitor: daemon is starting
Aug  1 00:23:18 hour monitor: ntp is not syn
Aug  1 00:23:35 rc_service: httpd 446:notify_rc restart_dsl_setting
Aug  1 00:23:40 pppd[1095]: Timeout waiting for PADO packets
Aug  1 00:23:48 hour monitor: daemon is starting
Aug  1 00:23:48 hour monitor: ntp is not syn
Aug  1 00:24:10 rc_service: httpd 446:notify_rc restart_dslwan_if 0
Aug  1 00:24:11 pppd[1095]: Unable to complete PPPoE Discovery
Aug  1 00:24:18 pppd[1131]: pppd 2.4.7 started by admin, uid 0
Aug  1 00:24:20 hour monitor: daemon is starting
Aug  1 00:24:20 hour monitor: ntp is not syn
Aug  1 00:24:31 zcip client: configured 169.254.86.253
Aug  1 00:24:48 hour monitor: daemon is starting
Aug  1 00:24:48 hour monitor: ntp is not syn
Aug  1 00:24:53 pppd[1131]: Timeout waiting for PADO packets
Aug  1 00:25:18 hour monitor: daemon is starting
Aug  1 00:25:18 hour monitor: ntp is not syn
Any help is much appreciated!

[#4]

Install latest firmware? https://www.asuswebstorage.com/navigate/s/2304B461198C4EDEA4AE8B963E2AFB2F4 this is latest beta.
When this is complete hold reset button for about 6 seconds on the back of router.  Dont use the quick internet setup it is very buggy fill it all manually at http://dsl-ac68u/Advanced_WAN_Content.asp make sure you use the correct PPP username and password.

[#5]

I have the same router and it works perfectly so hang in there
Let me log in to mine and I'll get you a copy of my settings - not sure if you can do it on this router but if you can edit the config files when exported but  I'll try that.

[#6]

ok just noticed you're on firmware 1.something.old - I'm pretty sure there are problems with VDSL on that version so make sure you get it updated before you do anything else. You can download the firmware from Asus and upload it to the device (once you're connected you can do it automatically but that's not much help to you yet).
If you just want to get online and happen to have an Openreach modem, you can set the Asus to use that - do the automatic firmware update and then setup the internal VDSL modem.
If you've got the modem and want to do it this way - it's pretty easy. Like redbull2k14 said, ignore the quick internet setup option as it's kinda broken (until you update the firmware anyway).
Go the main page and under Advanced settings - go to WAN.
Set the WAN connection Type to PPPoE
Enable WAN: Yes
Enable NAT: Yes
Enable UPnP: Yes
Get WAN IP automatically: Yes
Connect to DNS server automatically: Yes
PPP Username: your plusnet username + @plusdsl.net
Password: your password
Click apply and it'll have a think for a few minutes. Now would be a good time to connect up your Openreach modem if it's not already connected (so phone lead connected to openreach DSL port and Asus router LAN1 to LAN1 on openreach).
If all is well, you should have internet access.
If you get online this way - great! Get the router upgraded and then try the settings for the internal VDSL modem.