You encounter iTunes error 3194 when trying to restore or upgrade your iPhone. It can either be due to a wrong firmware version, the iOS version you are installing has not been approved by Apple or you are using a jailbreak tool to upgrade your iPhone.
However, this can be fixed by making changes in your system's host files. You can also perform a factory reset to fix iTunes error 3194. In case of data loss and absence of backup, make use of Stellar Data Recovery for iPhone to get all the lost data back. Read more