What message to you get when you try to access the site? For example, not able to create a secure connection, the red warning page for an attack site, etc. If you can copy/paste from the error page text, that would be helpful (here at https://support.mozilla.org/questions/1416485 - not by email).

No msg. The URL just disappears from the screen

If you click a link to the site in search engine results (on Google or Bing or DuckDuckGo), does Firefox follow the link or does it just do nothing?

Do you use a bookmark or are you starting with the main (home) page of this website?

If you use a bookmark to access a specific page then instead navigate to this page starting with the main page or with the sign in page in case there is a problem with this bookmark.

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose, make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website, data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

No matter how many times I clear Firefox history or try to use a Private Window, I get the same result. Firefox refuses to take me to SurveyHoney.

No matter how many times I clear Firefox history or try to use a Private Window, I get the same result. Firefox refuses to take me to SurveyHoney.

I assume that was using the address bar. What about a search result link to the site:

If you click a link to the site in search engine results (on Google or Bing or DuckDuckGo), does Firefox follow the link or does it just do nothing?

You can do a malware scan just to be sure.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware