try the following to increase the storage for kept history entries inside firefox:

enter about:config into the firefox location bar (confirm the info message in case it shows up), then right click somewhere in the page & create a new integer preference with the name places.history.expiration.max_pages & a very high number as value (which is the equivalent of the number of history entries that should be stored before they begin to expire)...

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

If you use cleanup software like CCleaner then check the settings for the Firefox application.

Also check the settings here:

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] Clear history when Firefox closes > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.