I always turn it off when I have used a g/n router. I looked at another post listed about the best router and a few people seem to do the same.
The first time I used one I forgot to put the latest firmware on both the extender and the pronto and I could not connect either.
I also removed any password so all I needed was the ssid.
Hope you don't think I trying to teach you to suck eggs but I found the basics are normally the problem.
Once i got connected then I added the password in. By the way you never mentioned wep or wap.
Also sometimes I had to set a stattic ip on the pronto, which I always do now as I hope good practice.