Can you go to this address in your web browser?
https://archives.paratext.org/send_receive_server/api80/listrepos
If you get a popup asking for a user name and password, the connection is working.
If the browser says the page does not exist or the server is not responding then something is wrong with your connection.
Do you have the program Covenant Eyes installed? That has been known to block Paratext send/receive to the Internet.
If the proxy setting RSquared found is from malware, it may have gotten reinstated. Have you run an antivirus and anti-malware scan?