Using WinSCP 5.1.9 (Build 10905) on Windows 10 protocol FTP in Commander mode
Initial Error message: "Lost Connection / Disconnected from server"
WinSCP is working fine for a while, then when I return after one of my 1-minute pauses, WinSCP has reported the error, then on Reconnect I get "Connection Failed, Access denied" and I can't get WinSCP to work until maybe a very long time later.
My keepalives button is not checked, and I can loose the connection sometimes with only a minute between activity. Other times, I can go for many minutes with no activity and WinSCP is still working. Also, once I lose connection, I can no longer make a WinSCP connection unless I don't try for a very long time.
I've now tried it with "keepalive" both checked and unchecked and get the same problem. I've talked with my website host and nothing has changed on their end in the past couple of weeks which is when I started running into the problem. Maybe I should completely uninstall, then install WinSCP? That would be a pain because I'll need to write down all my connection criteria.
Ah-ha! I managed to find an FTP site on a different web host and the connection seems to work fine, so now I'll let it sit for a bit and see if it fails.
You wrote before that "My keepalives button is not checked", so I've understood that you did not try it.
Anyway, if keepalives did not help, there's not much you can do on WinSCP side. Reinstalling won't help. If you want us to look further, please post a session log file with keepalives enabled. But I do not think we can help you much more here.