Hi destiny_soul, support volunteers are here for you, but first, did you already back up that previous.jsonlz4 and other contents of the sessionstore-backups folder to a safe location? If you haven't already could you use my Scrounger tool to extract a list of the file contents to confirm that it has what you're looking for. You can drag-and-drop the file onto the white box in the page and then click Scrounge URLs. If you don't get results within 30 seconds, close the tab and try again: https://www.jeffersonscher.com/ffu/scrounger.html If the list is useful, you can use the Save List button to back up the list in an HTML document (a web page) for future reference. The steps to persuade Firefox to actually use the old file are more involved. If there's one you want to try -- what have you tried so far? -- let us know.