No problem here. Try to rename the cert9.db file (cert9OLD.db) and remove a possible previously used cert8.db file in the Firefox profile folder with Firefox closed to remove intermediate certificates and exceptions that Firefox has cached. *https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean If this has helped to solve the problem then you can remove the renamed cert9OLD.db file. Otherwise you can undo the rename and restore cert9.db. You can use the button in "Help -> More Troubleshooting Information" (about:support) to go to the current Firefox profile folder or use the <b>about:profiles</b> page (Root directory). *Help -> More Troubleshooting Information -> Profile Folder/Directory:<br>Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data