I've never heard of the "Pee-post" but it sounds like a great invention! But I'm old-school (because I'm old! LOL!) and my questions/suggestions are old school. First, have you cleaned your carpets completely? I mean by using a pet strength carpet deodorizer. You can buy some good ones at Petco or probably any pet store...I don't know how well the supermarket mass market brands actually work. Dogs noses are so much better than ours. She will go where she smells previous pee so the smell must be completely obliverated.
Also, I know you said you take her out for a long time. Do you talk to her while she is out? If you do, don't. No playing when it's pee time!! Let her out, ignore her until she pees and then reward her. If she doesn't, give her 5 or 10 minutes, bring her back inside. Once she tries to go again, bring her right back outside. No talking or playing!!! Repeat a phrase. I use "Hurry up" When I say that, Duncan goes almost immediately (after 4 years of doing it though)
If she still doesn't go, repeat. Eventually she will associate the words with being outside and peeing. (Make sure you say it while she is actually DOING it) Dogs learn fairly quick and I'm sure she will pick it up. Good Luck.