Thank you for your post.
First, make sure the Wi-Fi or 3g network connection is working. In the FileMaker Go home screen, to the right of Remote Files and Hosts, tap the right icon (disk with a plus sign) to add a host. Enter the IP Address of the host machine. The host machine will now be listed under Favorite Hosts. Tap the host and see if any database files are open. If not, make sure the file is open in FileMaker Pro 12 and you have not only turned on Network Sharing, but also set the file to be accessible by all users. Then, try accessing again.
If you are still unable to see any FileMaker Pro hosted files, tap the other icon (disk with a magnifying glass) to see what other Local Network Hosts are hosting FileMaker Pro files.
If you are still unable to see files, try switching to an Ad Hoc network (computer-to-computer Wi-Fi network) and try again.
Keep me updated with any progress.