I have been having this issue for a while now. I will get this message on different websites, and then if I try again later it might work. It seems like it's a random chance of me getting this error. I have tried "about:config" commands as suggested on other posts on this forum and they didn't work. I checked my licenses, proxy settings and still nothing. I got another web browser to see if it's my PC or Firefox, and the other browser worked just fine. I am guessing there is something I need to do within Firefox, but I am not sure what that is.