Hi Carlos,
I known that there are some general network connect issue on iOS 11.
Apple device with IOS 11 having general network connect issues
https://gtacknowledge.extremenetworks.com/articles/Solution/Apple-device-with-IOS-11-having-general-...
Can you confirm whether your Apple devices are able to connect properly to non 802.1X authenticated WLANs (open or PSK)?
Also, please try to disable either "Management Frame Protection" or "Fast Transition" and confirm whether the devices are able to connect properly.
If it is not helpful, kindly request you to open the case to our GTAC.
Best regards
Bin