Sorry, I will describe the problem more correctly: the Firefox address bar for some websites works normally (e.g. "nytimes.com" takes me to nytimes.com) and for other websites (e.g. "treesforwatertown.org" doesn't send me anywhere at all, with no destination URL displayed in the status bar. However there's no problem getting to the same website if I navigate there from duckduckgo.  ??

Have you turned off Better Privacy, Adblock & HTTPS Everywhere and tried to go places ? If so ? ? Can try trouble shooting the extensions if think you have issues with them: https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems?redirectlocale=en-US&redirectslug=Troubleshooting+extensions+and+themes

Can try this : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Please let us know if this solved your issue or if need further assistance.

Do you have history items for websites that aren't working if you do a search in the Library or in the History sidebar?

If that is the case then try "Forget About This Site" in the right-click context menu.

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Command + Shift + R" (Mac)
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)

Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

• Firefox -> Preferences -> Advanced -> Network -> Cached Web Content: "Clear Now"

"Remove the cookies" from websites that cause problems.

• Firefox -> Preferences -> Privacy -> "Use custom settings for history" -> Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems