Thank you for your post.
If none of the iPad are able to connect, then this would probably be a network issue. However, since one of the iPad users can connect, something else is occurring. First, exit FileMaker Go to clear out any possible memory issue and relaunch. Try connecting at this point. If you still cannot connect, then the Wi-Fi on that iPad may have some interference. Try rebooting the iPad to reset iOS. Then, launch FileMaker Go and connect to the hosted file. If you still cannot connect, the host network may be compromised. Quit and relaunch FileMaker Pro, and then open the database file.
Keep me updated with any progress.
Hmmm, wouldn't you also get this error message if the WiFi is down or the WiFi signal is too weak due to either being too far away from the WiFi antenna or in a "dead zone"? (Dead zone = a place where an obstruction between you and the antenna blocks/weakens the radio signal from the WiFi antenna.)
Yes, you would get this message if the Wi-Fi signal is weak. For some reason, I assumed the two iPads that could connect were in similar proximity to the third non-working iPad. I should have asked that question first. Good call!