Click the three-horizontal-line icon in the upper right corner of your Firefox window. On the menu that appears, click on Options.
On the Options Box that pops up, click the Privacy Tab at the top of the box. Under the History section, you will see options for “Firefox Will:”. Make sure Remember “Remember History” is selected. Then, you will see a link for “clear your recent history”. Click that link.
When the Clear Recent History box opens, make sure all the check boxes are checked and then click the Clear Now button at the bottom.
Then click the OK button at the bottom of the Options box to close it. Finally, close Firefox then re-open Firefox and give it another try.
If you are still having trouble with Firefox, you may want to Reset/Refresh the browser. Click here for instructions on how to refresh your Firefox.