Apple released the first beta for iOS 11.3 just under a week ago after announcing what to expect a day earlier. Unlike most point releases, this is actually a mid-stream feature update, which is common at the halfway point between major releases.
As was to be expected, the public beta came with a few known issues. For example, Skype crashes on launch, so if that"s an app that you heavily depend on, you might want to sit this one out. However, other users are reporting that the 11.3 beta is refusing to connect to WiFi networks. Users are saying that the problem is with secured networks, because their units can easily connect to open/unsecured ones.
A few examples of the issues can be viewed below, from the Apple Support Communities and MacRumors:
my iPad Mini 2 with 11.3 Public Beta can connect with my wifi network now. But, I must to turn off my wifi password first on router settings
Same issue here. I have an iPad Air, and after updating the software it would no longer log in to any of my wi-fi networks or iCloud account.
First any WiFi with encryption password does not work (WEP, WPA2). Open WiFi works (with or without captive portal)
Other users reported success at connecting to open WiFi:
I am having the same issue, although I created a unsecure Wifi network (locked down to MAC address) and it connects. Another problem I have come across since the 11.3 (15E5167f) update, it wont accept my apple ID password “verification failed” so other issue there. Awaiting fix!
I was able to by pass the wifi by going to public wifi without any password….the problem with 11.3 beta is the apple ID verification process….it failed even after reset all settings.
At least one person was contacted by Apple for more information about the bug, but that person already downgraded to iOS 11.2.5. If you’re also facing this connectivity problem after installing iOS 11.3 beta 1, you will need to revert back to a stable build, or wait for the beta 2 release.
Source: Apple via MacRumors & PiunikaWeb