Did the technician ever return and fix your machine? I don't know why someone would modify HTTP settings when setting up a scan destination via FTP. I took a look at a 7845 and at the control panel the only relevant option that I have is to disable or enable the HTTP service. If that was toggled then it says that it will turn off HTTPS, which is how I would normally recommend accessing the site if that is enabled in your situation. If this isn't resolved yet here are a few things to try. In your web browser browse to.
http://<device ip>:21 - that should try to load the site using port 21.
https://<device ip> - If HTTPS is enabled that will load the HTTPS site which uses port 443. When HTTPS is enabled, but not forced, the home page will try to load over HTTP and then switch to HTTPS when required, usually after an admin login.
If none of that works then an alt-boot software reload might be required.