Firefox button > Options --> Privacy - History = un-check Permanent Private Browsing mode

See also:

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

Also make sure that you do not start Firefox with the -private command line switch.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions 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.com/kb/Safe+Mode

thank you, easy when you know where to look