either blocked you, or changed their passkey.
A few days ago my Acer laptop (Windows 8.1) stopped being able to connect to wifi networks, including ones I previously had no problem with. Right now I can connect by plugging my laptop into my iPhone and using it as a mobile hotspot, but that's it. I didn't change anything major before that, but to be safe I restored the system to about a week ago and the problem persists. I've made sure my drivers are up to date, run all the scans I can though Norton 360, and run all the windows troubleshooters to no avail. It says my wireless adapter is working properly, so at this point I'm at a loss.

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