M.Dlny

I had a similar problem - still not sure what caused it or how it fixed itself. I am using Firefox 84, Kaspersky 21.3. Kaspersky updated itself and I could not open anything in Firefox (everything worked fine in other browsers). I went through this thread, checked every option mentioned, turned on the option to stop checking encrypted connections. Then I saw that my Firefox version was out of date - updated it to the recommended 87 and now (knock on wood!) everything is back to normal.