Hi

This support article should help:

https://support.mozilla.org/en-US/kb/secure-connection-failed-firefox-did-not-connect

The PR_CONNECT_RESET_ERROR code indicates that the web server or an intermediary -- that might be security software, parental control software, a corporate proxy server, your internet service provider, a protective service the sites uses to block bot attacks, or something else -- sent Firefox the RST code to immediately stop trying to connect.

It can be challenging to track down why Firefox received this code. If you notice a pattern of various sites affected by the RST problem, it could indicate a change on your system, your network, or by your internet service provider. If it's just this one site, hmm, you could try clearing your cookies just for that site through the "Manage Data" button on the Settings page.