Help setting up Asus RT-N66U in repeater mode with Pace 5268AC

I had been able to set my Asus RT-N66U (ver. B1) up in repeater mode very easily with Xfinity's Arris TG862. However, since switching to Uverse, I have been unable to get it functioning correctly with the Pace 5268AC.

I have been able to connect the Asus to the 5268 (on both the 2.4 and 5G) and I am able to then connect to the Asus, however there is no internet connection making it through to the Asus from the 5268.

Any help is gratefully appreciated.

Thanks,

Phil