Perhaps you could give more details and explain what is blocked with the full details or a screenshot of the error message. Most Macs are still supported up to the current Fx48 Release * [[Firefox support has ended for Mac OS X 10.6, 10.7 and 10.8]] ** https://www.mozilla.org/firefox/organizations/faq/ It is only after support for Fx48 ends that it is necessary for you to drop down to the special ESR Fx45 . That is currently Fx45.'''3'''.0 not 45.'''0'''.3