When Always use private browsing mode is selected in Options > Privacy, that is the way Firefox is designed to work - no purple button and the Stop Private Browsing menu item is greyed-out.

Thanks for the answer but as I said in the question, I have already unchecked the "always use private browsing" button and any other privacy settings in the options menu area that might be causing this behavior. Do you have any other suggestions?

Are you using Firefox/Tools > Start Private Browsing?

• https://support.mozilla.org/kb/Private+Browsing

You may have an extension or theme that isn't working properly.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

You were correct. I found the offending extension and removed it. Thanks

You're welcome.

Can you tell us which extension caused it?

it was Instant Fox

Thanks.