<i>duplicate of [/questions/1489982] thread</i> I have the latest Mozilla Firefox download after uninstalling the prior version and re-downloading the latest on my windows 10 PC 3 times. I did this after my sign in to AT&T web mail failed to allow me to sign in. I had cleared cookies and cache. I get a window from AT&T saying "somethings gone wrong and try resetting your WiFi" when signing in. I am able to use the Mozilla browser to get to other websites including Yahoo or AT&T. I talked to AT&T and they had me sign into my webmail using MS edge. No problem, and also using MS explorer browser. They said Mozilla browzer was the problem. Anyhelp on solving this will be appreciated.