To clear a cached password, please follow the steps below (the example used here is for the Guest Wi-Fi:

Click the Wi-fi icon (1)
Select Network & Internet settings (2)

Select Wi-Fi (3)
Click Manage Known Networks

Finally, browse to TWOA_Guest and click Forget (5)

Now try connecting to TWOA_Guest again (please check with your Kaiako or Campus reception if unsure of the Guest Wi-fi password)