This error is found in a few scenarios, you can fix it with this solution. Firstly uninstall the app, and reinstall it again. After that enable your mobile data, then clear data and cache by going Settings > Apps > Zedge >Storage > click on clear data and then click clear cache. Finally, open the app and use your email for it. If this won't work, first force stops the app and then clear the cache. At last, restart your mobile. Or there is a chance that the Zedge Application server is low, wait for some time and try again.