Proxy error while trying to connect to FTP/computer, but proxy is not enabled already

I'm using Lenovo A7000's inbuilt application. Everything was fine, but suddenly, I am getting an error while trying to access the default FTP service via WiFi. > > > The folder 'ftp://192.168.1.3:2121' is read-only because the proxy server is not set up to allow full access. No proxy is set up on WiFi neither on my Android nor Windows PC. And, I am on the same network. I've verified using another phone, so it's unlikely the Windows problem. (Moreover, Xender is not working too. When I tap on connect to PC, my computer's browser showed an error unable to connect).