I have moved your query to the Adobe Photoshop Touch forum. The experts here are better placed to help you.
I'm sorry to hear that you have trouble accessing Facebook via PSTouch.
Here is a forum thread which describes a workaround for the issue.
When you go to your Facebook Acount Settings in a browser. Choose "Security" and disable "Secure Browsing" for a moment.
After that you should be able to login to Facebook within PSTouch.
Enable "Secure Browsing" again