Ipad disconnects from wifi when trying to log on

when trying to log onto a known wifi network, ipad manages to connect for a split second and then the wifi symbol disapears from the top right corner and it disconnects from the wifi network, but the network is still checked on the list below.

I have tried to turn wifi off and on, and I have tried "forgetting" the wifi network and log in again.

I have tried on different wifi networks and its the same behavior.

I have restarted both router and ipad.

I have done a hard reset on ipad.

I have reset all network settings on ipad.

I have updated software on ipad.

Still the ipad does not want to say logged onto the network.