WPA2 Password for MacBook Air (suddenly requires it - can't find anywhere)

Hi I've seen this question posted elsewhere but not with a solution that works. Help much appreciated as, like many people, I am trying to work from home at the moment!

My mac has worked on the wifi for weeks but suddenly requires a WPA2 password, which is not written on the box and the landlord doesn't know. Other devices are connected so it is working. The mac also asked for a WPA2 password for my neighbour's wifi, but I was able to get around this by putting the normal access password in on my iphone and then sharing it to my mac.

Is there please anyway of just using the normal password again like other devices? I have tried turning everything on and off again numerous times and have also run a diagnostic via neighbour's wifi, in case that's helpful.

It's driving me nuts! Thanks.

Running Catalina 10.15.4