Ty problémy jsou na netu poměrně časté a většinou bez řešení - týká se to iPadů. Co jsem našel:

Below is a User Tip about Wi-Fi issues. Suggest starting from the top and working down. Maybe one of them will help.

1) Perform a Forced Restart: Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow device to restart.
2) Reset Network Settings: Settings > General > Reset > Reset Network Settings. Rejoin the Network again.
3) Reboot Router/Modem: Unplug from power for 2 minutes and plug again. Update Router Firmware (check manufacturer’s support website for a newer FW). Also try different bands (2.4 GHz and 5 GHz) and different bandwidths (20 MHz recommended for the 2.4 band).
4) Change to Google's DNS: Settings > Wi-Fi > Click on the Network, Delete all numbers under DNS and enter 8.8.8.8 or alternatively 8.8.4.4
5) Disable device prioritization on the router if this feature is available. Also disable any VPN apps and test Wi-Fi again.
6) Backup and Restore the Device using iTunes (ask for additional for details if desired).

https://support.apple.com/en-us/HT201252
User Tip: https://discussions.apple.com/docs/DOC-9892