Changes to Certificate Trust settings when logging onto university wifi not working

I wiped my laptop because I wanted to sell it.

Apparently too much was wiped and the whole operating system is gone. I cannot connect to the internet to redownload it because im trying to connect to a WPA2 connection and everytime I put in my username and password the error "You are making changes to your certificate Trust Settings. Type the name and password of the user in the "(null)" group to allow this."

My username and password for the computer is not working. There is no other user, ive tried "never trusting" and all that on the certificate but nothing is working. Please help.

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