This situation happened after I updated to the latest version of Firefox at Play Store. Once I connect to the VPN, every website only shows this error and refuse to open normally. After I uninstalled and reinstalled it, nothing changed even I also cleared the cookies and cache. And then I downloaded the extension called FoxyProxy and selected it's proxy type as system, but it showed that system settings is not supported due to Firefox limitation. I didn't change anything, a few days ago everything went well, but it just happened suddenly without any notice. Other browsers are fine except Firefox. Please advise. Thanks for your assistance.