Hello Mahmud - I'm assuming that you mean you cannot access the forum using the iPF app on your iPad - correct? Are you able to use other Wi-Fi functions/apps (e.g. mail, web browsing, etc.) on the device? If so, then I would first close the offending app - open the multi-taskbar, hold your finger on the offending app, which should start to wiggle - press the x to close the program; return to home and re-open the app.
If that maneuver does not correct the issue, then restart your iPad, and if still not successful, resent your iPad - if none of this works, please post back - good luck!