when i select firefox on my macit says file not found and I have to enter private browsing to get a search window.

I need to find a way to have firefox search to load from doc without error message saying file not found and having to select private browsing a second time. It is not helpful when you ask a question and 90 or 2000 results come up. Calling your help center isn't designed for average users who do not understand and cannot follow directions that are not always clear. Please help me this error causes several extra steps each day.