I have a flatting situation with Ultrafast cable. One of my flatmates has got a new PC laptop and for some reason everytime he tries to login to our Wifi network, it won't accept the password. The other two of us have had no problems & can login on computer or mobile phone. What can be done, as it looks like it should be straitforward. Also he said he can go elsewhere in town and sign ito other wifi networks - like at his work. It's just our home one that is not working for him.
do you have 2.4g and 5g ? i had a similar issue and only way i could get round it was using a different connection either create a 5g one or use the guest option in your modem 192.168.1.1 setup , hope this helps im not techie though.