GT90H will not find networks

I am really confused by my sons GT90H tablet and am desperate for some advice as this is the second one we've bought and having the same problem.
We have been able to turn the wifi on for about an hour, then all connections disappear. When you try to turn it back on the 'switch' icon moves to the on position, but won't highlight blue or allow the tablet to respond and even though the switch says on, in the middle of the screen it says we need to turn on wifi to find networks. PLEASE can someone help, this has been driving me crazy since December 😫 really am clueless with all this so hoping I've posted in the right place too!

I can't work out how to shrink the pictures down as doing it from an iPhone and am far from tech savvy! Any ideas? Thank you SO much for replying, have got everything crossed that you have a solution! Have tried factory resetting though and hasn't made any difference

Not sure if this has come up but fingers crossed it has!

The switch does not change to show it is on, for example: it was highlighted blue when it was on and would search for connections but now it stays a grey colour when it is off and on and still says wi-fi needs to be turned on to find connections, no matter where the switch is. I'm sorry the photos aren't very clear, have tried with lights on and off but doesn't make a lot of difference!